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**Alienis Back** Wow...wait. How did you do that? I mean the formulae for the perfect square trinomials are

$\displaystyle (a+b)^2=a^2+2ab+b^2$ or

$\displaystyle (a-b)^2=a^2-2ab+b^2$

Which is the same as:

$\displaystyle a^2+2ab+b^2=(a+b)^2$ or

$\displaystyle a^2-2ab+b^2=(a-b)^2$

And then I thought of $\displaystyle y^2-3y-4$ as being equivalent

to $\displaystyle y^2-3y-2^2$ and therefore:

$\displaystyle y^2-3y-4$ should have been equal to $\displaystyle (y-2)^2$ but this didn't fit into my solution.

After that I noticed that according to the formulae, in a perfect square, the last term, b, should alway be positive while mine, -4, is negative. How did you know it is a perfect square trinomial when it doesn't match these formulae and how did you factor it??

Just hope there are not too many questions...It is only that an answer now will solve many questions in the future.