How to simplify an expression that does not have a common factor I am trying to simplify this expression :
$$9a^4 + 12a^2b^2 + 4b^4$$
So I ended up having this :
$$(3a^2)^2 + 2(3a^2)(2b^2) + (2b^2)^2$$
However, after that I don't know how to keep on simplifying the equation, it is explained that the answer is $(3a^2 + 2b^2)^2$ because the expression is equivalent to $(x + y)^2$ but I don't understand how they get to that ?

after the binomial formula $$(x+y)^2=x^2+2xy+y^2$$ we get: $$(3a^2+2b^2)^2=9a^4+12a^2b^2+4b^4$$
