Quadratic Equ. in One Unknown

Questions and Answers :

If the roots of 3x^2 + (k+3)x - 12 = 0 are numerically equal but opposite in signs, find the value of k.

1. What dose it mean? (numerically equal but opposite in signs)

It means that the roots are in the same as a number but in positive and negative. i.e. 9 , -9 ; 2 , -2

2. solve it, please.

Let β be one of the roots of the equation.

Sum of roots = - β + β

= 0

3x^2 + (k+3)x - 12 = 0

Sum of roots = [ - (k+3) ] / 3

[ - (k+3) ] / 3 = 0

- k - 3 = 0

- k = 3

k = - 3

Therefore, the value of k is -3 .