Question

Find two real numbers b such that the algebraic expression is a perfect square trinomial.
16x^2 + bxy +25y^2

Answer 1

http://images.flatworldknowledge.com/redden/redden-eq09_034.jpg

Answer 2

@saifoo.khan please explain your answer

Answer 3

Do you know how to do the completing square?

Answer 4

I now believe its 20 and -20.
I tried working it out again :

16x^2 + bxy + 25y^2
\[(16x ^{2} + 20xy) + (20xy +25y ^{2})\]
I got 20xy from doing a*c, 16 * 25. Which equals 40. And then i to the square root of that to get 20.

Answer 5

This then factors down to \[(4x+5y)^{2}\] which is a perfect square

Answer 6

You're right!

Answer 7

So b is going to be 40.

Answer 8

Oh yes thats right! Almost overlooked that

Answer 9

you know it can b -40 too, right ?

Answer 10

thts why they asked in the question, "two" values