Question 1208686
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The tutor ikleyn has a great answer. Here's another approach
{{{y^2 = 25}}}


{{{y^2-25 = 0}}}


{{{(y-5)(y+5) = 0}}} Difference of squares factoring rule a^2-b^2 = (a-b)(a+b)


{{{y-5=0}}} or {{{y+5 = 0}}}  If A*B = 0 then either A = 0 or B = 0


{{{y = 5}}} or {{{y = -5}}}


To check each answer, plug them into the original equation one at a time. 
Make sure the negative is being squared as well. 
If y = -5 then {{{y^2 = (-5)^2 = (-5)*(-5) = 25}}} and NOT {{{y^2 = -(5^2) = -1*5*5 = -25}}}
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