Question 154068
(a + b)^2 is not equal to a^2 + b^2. 
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Simply, in {{{(a+b)^2}}} means that you need to add the numerals (or variables)before raising them to the 2nd power.
In {{{(a^2 + b^2)}}} means that you need to raised the numerals or variables to the 2nd power then add them.</pre>
To prove, pick {{{a=1}}} and {{{b=2}}}
{{{(a+b)^2=(1+2)^2=3^2=9}}} is not equal to {{{a^2+b^2=1^2+2^2=1+4=5}}}
See www.mathsisfun.com/algebra/exponent

Thank you,
Jojo