JAMB - Mathematics (2024 - No. 41)
Find the roots of x\(^3\) - 19x - 30=0
-5, 3, and 2
5, 3, and -2
5, -3 and -2
-5, -3 and 2
설명
x\(^3\) - 19x - 30
test x = 5
5\(^3\) −19(5) − 30 = 125 − 95 − 30 = 0
(x - 5) is a factor.
x\(^3\) - 19x - 30 divided by (x - 5) = x\(^2\) + 5x + 6
factorizing x\(^2\) + 5x + 6, we have (x+2)(x+3)
(x+2)(x+3)(x - 5) = 0
x = -2, -3, and 5.