Question

What values of x would make the following equation true?

Answer 1

There are many ways to do this. Such ways are using the quadratic formula, completing the square, etc.
We have $x^2+10x-21=0$ We can add 46 to both sides so the -21 becomes a +25. by doing that, we get $x^2+10x+25=46$ This can be wrote as $(x+5)^2=46$ We solve the square root and get $(x+5)= +-\sqrt{46}$ (The +- is a plus minus sign.) Subtract five on both sides to get $x=-5+- \sqrt{46}$
The answer is C.

Answer 2

There are many ways to do this. Such ways are using the quadratic formula, completing the square, etc.

We have  We can add 46 to both sides so the -21 becomes a +25. by doing that, we get  This can be wrote as  We solve the square root and get  (The +- is a plus minus sign.) Subtract five on both sides to get  

The answer is C.