how do you solve a quadratic equation by completing the square if the equation is not equal to 0?

Question

How do you sove this eqation x²- 4x - 91 = 7 by completing the square?

Answer 1

The answer is +/root (102)

Answer 2

you can always make the equation equal to zero...

 

lets try completing the square

 

x²- 4x - 91 = 7

 

x²-4x = 98

x² -4x +4 = 98+4    (to complete the square, divide the x term by 2, and square it)

                                When you add 4 to one side, you must add 4 to the otherside as well

 

(x - 2)² = 112

 

x - 2 = +/-root(112)

x = 2+ root(112) , 2-root(112),  (you can also factor out 4² from the radical)