Question 935045


{{{437 = (21 + x)(21 -x)}}}, 

{{{437 = 21^2 -x^2}}}

{{{437 = 441 -x^2}}}

{{{x^2 = 441 -437}}}

{{{x^2 = 4}}}

{{{x = sqrt(4)}}}

{{{x = 2}}} or {{{x = -2}}}