How do you factor $x^2 + 5x + 4$ ?

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Answer 1 · 2015-05-16T12:56:45

Notice that $5 = 1+4$ and $4 = 1*4$ , so this can be factored as follows:

$x^2+5x+4 = (x+1)(x+4)$

This is an instance of a general observation that

$(x+a)(x+b) = x^2+(a+b)x+ab$

How do you factor x^2 + 5x + 4x^2 + 5x + 4?