Posted by Shadow on Sunday, March 25, 2012 at 9:52pm.
What positive value of b makes 9^2bx+4 a perfect square trinomial? How would you solve this problem? Thanks

Math  Shadow, Sunday, March 25, 2012 at 9:52pm
9x^2bx+4

Math  Reiny, Sunday, March 25, 2012 at 10:07pm
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

Math  Shadow, Sunday, March 25, 2012 at 10:11pm
Thank you!

Math  Reiny, Sunday, March 25, 2012 at 10:17pm
Welcome
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