posted by Shadow on .
What positive value of b makes 9^2-bx+4 a perfect square trinomial? How would you solve this problem? Thanks
First of all to be a perfect square, the first and last terms should be perfect squares, and they are!
so it looks like we had
(3x ± 2)^2
for (3x+2)^2 we would get 9x^2 + 12x + 4
so -bx = 12x
b = -12
for (3x - 2)^2 we would get 9x^2 - 12x + 4
so -bx = -12x
b = 12
So b = ± 12