Question

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

Answer 1

$\frac{1 +/- \sqrt{253} }{14}$

You can get this by using the quadratic equation with a = 7, b = -1, c = -9

Answer 2

we know that

The formula to solve a quadratic equation of the form $ax^{2} +bx+c=0$ is equal to

$x=\frac{-b(+/-)\sqrt{b^{2}-4ac}} {2a}$

in this problem we have

$7x^{2}=9+x$  

Equate the equation to zero

$7x^{2}-x-9=0$  

so

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

substitute in the formula

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

$x=\frac{1(+/-)\sqrt{1+252}} {14}$

$x=\frac{1(+/-)\sqrt{253}}{14}$

therefore

the answer is

$x=\frac{1(+/-)\sqrt{253}}{14}$