Question

A whole square + b square hole

Answer 1

Answer:

aa+bb=(a+b)(a+b)-2ab

=aa+bb

Answer 2

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You can find (a+b)2 by the following method:

$\bf{(a+b)2 \: = \: (a+b) \times (a+b)}$

Now,

$\bf{(a+b) \times (a+b)=a^2+ab+ba+b^2}$

By commutative property of multiplication,ab=ba

So,

$\bf{=> a^2+ab+ba+b^2}$

$\bf{=> a^2+2ab+b^2}$

Hence,

$\bf{(a+b)² = a^2+2ab+b^2}$

Few more formula -

$\bf{(A-B)² = A²+B²-2AB}$