If the roots of the equation Ax^2 + Bx + C = 0 are -1 and 1

• Quant Quadratic

If the roots of the equation Ax² + Bx + C = 0 are -1 and 1, then which one of the following is correct?

1. A and B are both positive
2. A and C are both negative
3. A and C are of opposite sign
4. A and C are both zero

Answer

Putting the values -1 and 1 in the equation Ax² + Bx + C = 0, we get

A + B + C = 0 and A - B + C = 0

Subtracting the second equation from the first, we obtain

2B = 0 or B = 0.

So, A + C = 0 or A = - C.

Therefore, A and C are of opposite sign.

The correct option is C.