JEE Advance - Mathematics (2004)

• 1

  Find the equation of plane passing through $$(1, 1, 1)$$ & parallel to the lines $${L_1},{L_2}$$ having direction ratios $$(1,0,-1),(1,-1,0).$$ Find the volume of tetrahedron formed by origin and the points where these planes intersect the coordinate axes.

  回答

  (A)

  x + y + z = 3; 9/2 cubic units
• 1

  The area enclosed between the curves $$y = a{x^2}$$ and
  $$x = a{y^2}\left( {a > 0} \right)$$ is $$1$$ sq. unit, then the value of $$a$$ is

  回答

  (A)

  $$1/\sqrt 3 $$
• 2

  $${P_1}$$ and $${P_2}$$ are planes passing through origin. $${L_1}$$ and $${L_2}$$ are two line on $${P_1}$$ and $${P_2}$$ respectively such that their intersection is origin. Show that there exists points $$A, B, C,$$ whose permutation $$A',B',C'$$ can be chosen such that (i) $$A$$ is on $${L_1},$$ $$B$$ on $${P_1}$$ but not on $${L_1}$$ and $$C$$ not on $${P_1}$$ (ii) $$A'$$ is on $${L_2},$$ $$B'$$ on $${P_2}$$ but not on $${L_2}$$ and $$C'$$ not on $${P_2}$$

  回答

  (A)

  The statement is always true and can be proved using linear independence and suitable vector choices.
• 2

  If $$f(x)$$ is differentiable and $$\int\limits_0^{{t^2}} {xf\left( x \right)dx = {2 \over 5}{t^5},} $$ then $$f\left( {{4 \over {25}}} \right)$$ equals

  回答

  (A)

  $$2/5$$
• 3

  If $$\overrightarrow a ,\overrightarrow b ,\overrightarrow c $$ and $$\overrightarrow d $$ are distinct vectors such that
  $$\,\overrightarrow a \times \overrightarrow c = \overrightarrow b \times \overrightarrow d $$ and $$\overrightarrow a \times \overrightarrow b = \overrightarrow c \times \overrightarrow d \,.$$ Prove that
  $$\left( {\overrightarrow a - \overrightarrow d } \right).\left( {\overrightarrow b - \overrightarrow c } \right) \ne 0\,\,i.e.\,\,\,\overrightarrow a .\overrightarrow b + \overrightarrow d .\overrightarrow c \ne \overrightarrow d .\overrightarrow b + \overrightarrow a .\overrightarrow c $$

  回答

  B

  E
• 3

  If $$y=y(x)$$ and $${{2 + \sin x} \over {y + 1}}\left( {{{dy} \over {dx}}} \right) = - \cos x,y\left( 0 \right) = 1,$$
  then $$y\left( {{\pi \over 2}} \right)$$ equals

  回答

  (A)

  $$1/3$$
• 4

  where, $${\rm{z = x + iy, }}\alpha {\rm{ = }}\,{\alpha _1}{\rm{ + i}}{\alpha _2}{\rm{,}}\,\beta = {\beta _1}{\rm{ + i}}{\beta _2}{\rm{ }}$$

  回答

  (B)

  Centre = $$\frac{{\alpha - {k^2}\beta}}{{1 - {k^2}}}$$, radius = $$\frac{k}{{\left| {1 - {k^2}} \right|}}left| {\alpha - \beta } \right|$$
• 4

  If three distinct numbers are chosen randomly from the first $$100$$ natural numbers, then the probability that all three of them are divisible by both $$2$$ and $$3$$ is

  回答

  (D)

  $$4/1155$$
• 5

  A parallelopiped $$'S'$$ has base points $$A, B, C$$ and $$D$$ and upper face points $$A',$$ $$B',$$ $$C'$$ and $$D'.$$ This parallelopiped is compressed by upper face $$A'B'C'D'$$ to form a new parallelopiped $$'T'$$ having upper face points $$A'',B'',C''$$ and $$D''.$$ Volume of parallelopiped $$T$$ is $$90$$ percent of the volume of parallelopiped $$S.$$ Prove that the locus of $$'A''',$$ is a plane.

  回答

  (B)

  The locus of A'' is a plane parallel to the base ABCD.
• 5

  If $$\overrightarrow a = \left( {\widehat i + \widehat j + \widehat k} \right),\overrightarrow a .\overrightarrow b = 1$$ and $$\overrightarrow a \times \overrightarrow b = \widehat j - \widehat k,$$ then $$\overrightarrow b $$ is

  回答

  (C)

  $$\widehat i$$
• 6

  A box contains $$12$$ red and $$6$$ white balls. Balls are drawn from the box one at a time without replacement. If in $$6$$ draws there are at least $$4$$ white balls, find the probability that exactly one white is drawn in the next two draws. (binomial coefficients can be left as such)

  回答

  (E)

  $$(\frac{\binom{6}{4}\binom{12}{2} + \binom{6}{5}\binom{12}{1} + \binom{6}{6}\binom{12}{0}}{\binom{18}{6}}) \times (\frac{\binom{2}{1} \binom{10}{1}}{\binom{12}{2}})$$
• 6

  If the lines $${{x - 1} \over 2} = {{y + 1} \over 3} = {{z - 1} \over 4}$$ and $$\,{{x - 3} \over 1} = {{y - k} \over 2} = {z \over 1}$$ intersect, then the value of $$k$$ is

  回答

  (B)

  $$9/2$$
• 7

  $$A$$ and $$B$$ are two independent events. $$C$$ is even in which exactly one of $$A$$ or $$B$$ occurs. Prove that $$P\left( C \right) \ge P\left( {A \cup B} \right)P\left( {\overline A \cap \overline B } \right)$$

  回答

  (A)

  The statement is always true.
• 7

  The unit vector which is orthogonal to the vector $$3\overrightarrow i + 2\overrightarrow j + 6\overrightarrow k $$ and is coplanar with the vectors $$\,2\widehat i + \widehat j + \widehat k$$ and $$\,\widehat i - \widehat j + \widehat k$$$$\,\,\,$$ is

  回答

  (C)

  $${{3\widehat i - \widehat k} \over {\sqrt {10} }}$$
• 8

  A curve $$'C''$$ passes through $$(2,0)$$ and the slope at $$(x,y|)$$ as $$\,{{{{\left( {x + 1} \right)}^2} + \left( {y - 3} \right)} \over {x + 3}}$$. Find the equation of the curve. Find the area bounded by curve and $$x$$-axis in fourth quadrant.

  回答

  (B)

  Area = 4/3 sq. units, Equation: y = (x+1)^2 + 3ln|x+3| - 1 - 3ln5
• 8

  The value of the integral $$\int\limits_0^1 {\sqrt {{{1 - x} \over {1 + x}}} dx} $$ is

  回答

  (B)

  $${\pi \over 2} - 1$$
• 9

  Find the value of $$\int\limits_{ - \pi /3}^{\pi /3} {{{\pi + 4{x^3}} \over {2 - \cos \left( {\left| x \right| + {\pi \over 3}} \right)}}dx} $$

  回答

  (A)

  $$\frac{4\pi}{\sqrt{3}}\left[\tan^{-1}(3) - \frac{\pi}{4}\right]$$
• 9

  If $$\omega $$ $$\left( { \ne 1} \right)$$ be a cube root of unity and $${\left( {1 + {\omega ^2}} \right)^n} = {\left( {1 + {\omega ^4}} \right)^n},$$ then the least positive value of n is

  回答

  (B)

  3
• 10

  If $$y\left( x \right) = \int\limits_{{x^2}/16}^{{x^2}} {{{\cos x\cos \sqrt \theta } \over {1 + {{\sin }^2}\sqrt \theta }}d\theta ,} $$ then find $${{dy} \over {dx}}$$ at $$x = \pi $$

  回答

  (C)

  $2\pi$
• 10

  If $$f\left( x \right) = {x^a}\log x$$ and $$f\left( 0 \right) = 0,$$ then the value of $$\alpha $$ for which Rolle's theorem can be applied in $$\left[ {0,1} \right]$$ is

  回答

  (D)

  $$1/2$$
• 11

  Prove that for $$x \in \left[ {0,{\pi \over 2}} \right],$$ $$\sin x + 2x \ge {{3x\left( {x + 1} \right)} \over \pi }$$. Explain
  the identity if any used in the proof.

  回答

  B

  C
• 11

  If $$f\left( x \right) = {x^3} + b{x^2} + cx + d$$ and $$0 < {b^2} < c,$$ then in $$\left( { - \infty ,\infty } \right)$$

  回答

  (A)

  $$f\left( x \right)$$ is a strictly increasing function
• 12

  Using Rolle's theorem, prove that there is at least one root
  in $$\left( {{{45}^{1/100}},46} \right)$$ of the polynomial
  $$P\left( x \right) = 51{x^{101}} - 2323{\left( x \right)^{100}} - 45x + 1035$$.

  回答

  (C)

  P(45^(1/100)) = P(46) = 0, hence by Rolle's theorem, there exists at least one root in (45^(1/100), 46).
• 12

  The value of $$x$$ for which $$sin\left( {{{\cot }^{ - 1}}\left( {1 + x} \right)} \right) = \cos \left( {{{\tan }^{ - 1}}\,x} \right)$$ is

  回答

  (D)

  $$-1/2$$
• 13

  Tangent is drawn to parabola $${y^2} - 2y - 4x + 5 = 0$$ at a point $$P$$ which cuts the directrix at the point $$Q$$. $$A$$ point $$R$$ is such that it divides $$QP$$ externally in the ratio $$1/2:1$$. Find the locus of point $$R$$

  回答

  (A)

  (x - 1)(y - 1)^2 + 4 = 0
• 13

  The sides of a triangle are in the ratio $$1:\sqrt 3 :2$$, then the angles of the triangle are in the ratio

  回答

  (D)

  $$1:2:3$$
• 14

  Find the equation of circle touching the line 2x + 3y + 1 = 0 at (1, -1) and cutting orthogonally the circle having line segment joining (0, 3) and (- 2, -1) as diameter.

  回答

  (D)

  2x^2 + 2y^2 - 10x - 5y + 1 = 0
• 14

  If $$y$$ is a function of $$x$$ and log $$(x+y)-2xy=0$$, then the value of $$y'(0)$$ is equal to

  回答

  (A)

  $$1$$
• 15

  Prove by permulation or otherwise $${{({n^2})!} \over {{{(n!)}^n}}}$$ is an integer $$(n \in {1^ + })$$.

  回答

  (D)

  This is a classic combinatorial problem involving arranging elements with repetitions, yielding an integer result.
• 15

  If the line $$62x + \sqrt 6 y = 2$$ touches the hyperbola $${x^2} - 2{y^2} = 4$$, then the point of contact is

  回答

  (D)

  $$\left( {4, - \,\sqrt 6 } \right)$$
• 16

  If $$a,\,b,c$$ are positive real numbers. Then prove that $$${\left( {a + 1} \right)^7}{\left( {b + 1} \right)^7}{\left( {c + 1} \right)^7} > {7^7}\,{a^4}{b^4}{c^4}$$$

  回答

  B

  C

  D

  E
• 16

  If tangents are drawn to the ellipse $${x^2} + 2{y^2} = 2,$$ then the locus of the mid-point of the intercept made by the tangents between the coordinate axes is

  回答

  (A)

  $${1 \over {2{x^2}}} + {1 \over {4{y^2}}} = 1$$
• 17

  The angle between the tangents drawn from the point $$(1, 4)$$ to the parabola $${y^2} = 4x$$ is

  回答

  (C)

  $$\pi /3$$
• 18

  If one of the diameters of the circle $${x^2} + {y^2} - 2x - 6y + 6 = 0$$ is a chord to the circle with centre (2, 1), then the radius of the circle is

  回答

  (C)

  3
• 19

  Area of the triangle formed by the line $$x + y = 3$$ and angle bisectors of the pair of straight line $${x^2} - {y^2} + 2y = 1$$ is

  回答

  (A)

  2 sq. units
• 20

  An infinite G.P. has first term '$$x$$' and sum '$$5$$', then $$x$$ belongs to

  回答

  (C)

  $$0 < x < 10$$
• 21

  If $${}^{n - 1}{C_r} = \left( {{k^2} - 3} \right)\,{}^n{C_{r + 1,}}$$ then $$k \in $$

  回答

  (D)

  $$\left( {\sqrt 3 ,2} \right]$$
• 22

  For all $$'x',{x^2} + 2ax + 10 - 3a > 0,$$ then the interval in which '$$a$$' lies is

  回答

  (B)

  $$ - 5 < a < 2$$
• 23

  If one root is square of the other root of the equation $${x^2} + px + q = 0$$, then the realation between $$p$$ and $$q$$ is

  回答

  (A)

  $${p^3} - q\left( {3p - 1} \right) + {q^2} = 0$$
• 24

  Given both $$\theta $$ and $$\phi $$ are acute angles and $$\sin \,\theta = {1 \over 2},\,$$ $$\cos \,\phi = {1 \over 3},$$ then the value of $$\theta + \phi $$ belongs to

  回答

  (B)

  $$\left( {{\pi \over 2},{{2\pi } \over 3}} \right)$$