posted by Christian on .
Replace each of the question marks with a value that will make the polynomial a perfect square trinomial.
Could someone show me how to solve these?
Take the first:
factor out the 4
4( x^2 + 3x + ?)
take half the center term, and square it. half is 3/2, squared is 9/4
4( x^2 + 3x + 9/4)
Put the 4 back in...
4x^2 + 12x+9
Notice the last term is a perfect square, its square root is 9. Twice nine is eighteen.
Now to find the missing term, divide 90 by 18: five.
25x^2 + 90x + 81