Question 123457
solve {{{x^2+3x^2=18^2}}}
:
x^2 and 3x^2 are like terms, just add them together, square 18 to get 324
{{{4x^2 = 324}}} 
Divide both sides by 4
{{{x^2 = 324/4}}}
{{{x^2 = 81}}}
x = {{{sqrt(81)}}}
x = 9
:
:
Check solution:
9^2 + 3(9^2) =
81 + 3(81) =
81 + 343 = 324, which is 18^2