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 = (-b+/-√(b^2-4ac) )/(2a)`
Where,

`a = 7 b = -1 c = -9`
Substituting values we have:

`x = (-(-1)+/-√((-1)^2-4(7)(-9)) )/(2(7))`
Answer:
An equation that shows the quadratic formula used correctly to solve is:

`x = (-(-1)+/-√((-1)^2-4(7)(-9)) )/(2(7))`