Isolate the variable terms by
adding -10 to both sides:



To the side, multiply the coefficient of x by .
                      

Now square .  

Add  to both sides of this: 



Combine the right side: 



Factor the left side:



Write the left side as the square of
a binomial:



Take the square root of both sides,
remembering the ± on the right:



=

Add 5 to both sides:



Edwin