Question 111205
{{{x^2-225=0}}}
:
Yes, adding 225 to both sides is the correct first step.
:
{{{x^2=225}}}
:
Then take the square root of both sides, remembering to consider both the positive and negative square roots.
:
{{{x = 15}}} or {{{x = -15}}}
:
There is another way to solve this one, and that is to recognize that you are dealing with the difference of two squares, i.e. {{{a^2-b^2=(a+b)(a-b)}}}.
Hence: {{{x^2-225=0}}}
{{{(x+15)(x-15)=0}}}
Giving you the same result:
{{{x = 15}}} or {{{x = -15}}}