Math question help?

Question

What is the answer to this question: x^2-x+q=0 is -2, what is the other root?

Answer 1

Another approach, which might be handy if you are faced with tricker questions in the future, is to use the fact that in a quadratic equation, the coefficient of x is the negative of the sum of the roots, and the constant term is the product of the roots. (You don't need the latter fact for this problem.)

let r = other root

so -1= - (-2+r)
1= -2 + r
r=3.

I should clarify: this applies to quadratic equations in which the coefficient of x^2 is one. If it isn't, divide through by that coefficient before proceeding.

Answer 2

assume you meant -2 is one of the root

plug -2 in for x

(-2)^2 - (-2) + q = 0
4 + 2 + q = 0
6 + q = 0
q = -6

x^2 - x - 6 = 0

factor
(x + 2) (x - 3) = 0

x = -2 or 3

so the other root is 3

Answer 3

plug in -2 for x to solve for q
4+2+q = 0
q= -6
x^2-x-6=0
(x+2)(x-3) = 0
x = 3