JEE MAIN - Mathematics (2016 - 9th April Morning Slot - No. 10)

A circle passes through (−2, 4) and touches the y-axis at (0, 2). Which one of the following equations can represent a diameter of this circle?
4x + 5y − 6 = 0
2x − 3y + 10 = 0
3x + 4y − 3 = 0
5x + 2y + 4 = 0

Explanation

JEE Main 2016 (Online) 9th April Morning Slot Mathematics - Circle Question 129 English Explanation
EF = perpendicular bisector of chord AB

BG = perpendicular to y-axis

Here C = center of the circle

mid-point of chord AB, D = ($$-$$ 1, 3)

slope of AB = $${{4 - 2} \over { - 2 - 0}}$$ = $$-$$ 1

$$ \because $$   EF  $$ \bot $$ AB

$$ \therefore $$   Slope of EF = 1

Equation of EF, y $$-$$ 3 = 1 (x + 1)

$$ \Rightarrow $$    y = x + 4       . . . .(i)

Equation of BG

y = 2         . . . . (ii)

From equations (i) and (ii)

x = $$-$$ 2, y = 2

since C be the point of intersection of EF and BG, therefore center, C = ($$-$$ 2, 2)

Now coordinates of center C satiesfy the equation

2x $$-$$ 3y + 10 = 0

Hence 2x $$-$$ 3y + 10 = 0   is the equation of the diameter

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