Question

Find the roots of the quadratic equation $-x^2+7x-10=0$ using the quadratic formula.

• A. 3, 4
• B. 2, 5
• C. 5, 6
• D. 3, -5

Answer 1

The correct option is B

2, 5

Given equation is $-x^2+7x-10=0.$

On comparing with $a{x}^2+bx+c=0$, we get

a = -1, b = 7 and c = -10

By quadratic formula,

$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$

$\Rightarrow x=\frac{-\left(7\right)\pm \sqrt{(7{)}^2-4(-1\left)\right(-10)}}{2(-1)}$

$\Rightarrow x=\frac{-7\pm \sqrt{49-40}}{-2}$

$\Rightarrow x=\frac{-7\pm \sqrt{9}}{-2}$

$\Rightarrow x=\frac{-7\pm 3}{-2}=\frac{-4}{-2},\frac{-10}{-2}=2,5$

So, 2 and 5 are two roots of the given equation.