Question

Which equation shows the quadratic formula used correctly to solve 7x^2 = 9 + x for x?

Answer 1

To use the quadratic formula properly, you first would want to set your quadratic equation equal to zero by moving all terms to one side and combining like terms. That would look like: $7x^2-x-9=0$. Now, you can use the quadratic formula: $\frac{-b+ \sqrt{b^2-4ac} }{2a}$; note the "+" after the "-b" term should actually be a +/- as there are 2 answers to a quadratic. Last, plug in the correct numbers for a, b, and c to get your answer. $\frac{1+ \sqrt{1^2-4*7*-9} }{2*7}= \frac{1+ \sqrt{253} }{14}$