Answer:
x = -2, 3, -4.
Step-by-step explanation:
x^3 - 10x = -3x2 + 24 = 0
x^3 + 3x^2 - 10x - 24 = 0
The last term is 24 and the coefficient of x^3 is 1 so +/- 1, +-2, +/- 3 and +/- 4 could be among the roots ( by The Rational Root Theorem).
Let x = 1
f(x) = 1^3 +3(1)^2 - 10 - 24 = -30 so it's no t .
f(-1) = -1 + 3 + 10 - 24 = -12 so it's not -1.
Let x = 2:
f(2) = 2^3 +3*4 - 20 - 24 = -32 so its not 2
f(-2) = -8 + 12 + 20 - 24 = 0 so x = -2 is a root
and therefore x+ 2 is a factor and we divide:
x + 2 ) x^3 + 3x^2 - 10x - 24 ( x^2 + x - 12 <------ The quotient
x^3 + 2x^2
x^2 - 10x
x^2 + 2x
-12x - 24
-12x - 24
..............
Now x^2 + x - 12 = (x - 3)(x + 4)
So (x + 2)(x - 3)(x + 4) = 0
This gives
x = -2, 3, -4.
