Question

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

Answer 1

Answer is D on E2020

Answer 2

For this case we have the following quadratic equation:
 $7x ^ 2 = 9 + x$
 Rewriting the equation we have:
 $7x ^ 2 - x - 9 = 0$
 The quadratic formula to solve the equation is:
 $x = \frac{-b+/-\sqrt{b^2-4ac} }{2a}$
 Where,
 $a = 7 b = -1 c = -9$
 Substituting values we have:
 $x = \frac{-(-1)+/-\sqrt{(-1)^2-4(7)(-9)} }{2(7)}$
 Answer:
 An equation that shows the quadratic formula used correctly to solve is:
 $x = \frac{-(-1)+/-\sqrt{(-1)^2-4(7)(-9)} }{2(7)}$