Question

Which equation shows the quadratic formula used correctly to solve 7x2 = 9 + x for x?

Answer 1

The answer is the D :)

Answer 2

`x=\frac{1\pm\sqrt{(-1)^(2)+4(7)(9)}} {2(7)}`

Explanation:

we know that

The formula to solve a quadratic equation of the form

`ax^(2) +bx+c=0`

is equal to

`x=\frac{-b\pm\sqrt{b^(2)-4ac}} {2a}`

in this problem we have

`7x^(2) -x-9=0`

so

`a=7\\b=-1\\c=-9`

substitute in the formula

`x=\frac{-(-1)\pm\sqrt{-1^(2)-4(7)(-9)}} {2(7)}`

`x=\frac{1\pm\sqrt{(-1)^(2)+4(7)(9)}} {2(7)}`

`x=\frac{1\pm√(253)} {14}`