Question

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

Answer 1

Answer:

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

Step-by-step 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

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

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

$x=\frac{1\pm\sqrt{253}} {14}$

Answer 2

Answer:

The answer is the D :)