Question

If the roots of a quadratic equation are $-6$ and $7$, then the quadratic equation is

• A. $x^2+x+42=0$
• B. $x^2-x+42=0$
• C. $x^2-x-42=0$
• D. $x^2-x+21=0$

Answer 1

The correct option is C $x^2-x-42=0$

Let $\alpha =-6$ and $\beta =7$, then we know that quadratic equation is given as
$x^2-Sx+P=0$
$\Rightarrow x^2-(\alpha +\beta )x+\alpha \beta =0$
$\Rightarrow x^2-(-6+7)x+(-6\cdot 7)=0$
$\Rightarrow x^2-x-42=0$