math,help
posted by jasmine20 .
how do i find the following:
is there a formula for this?
Problem #15
Find the constant term that should be added to make the following expression a perfect square trinomial.
x^2+7x
square a few binomials and see if you can see a pattern
e.g. (x+3)^2 = x^2 + 6x + 9
(x7)^2 = x^2  14x + 49
notice the coefficient of the middle term is twice the square root of the last term
so you have to reverse the pattern
take 1/2 of the middle term number, then square it.
for your e.g.
x^2 + 7x + ???
1/2 of 7 is 7/2, which when squared is 49/4
so
x^2 + 7x
=x^2 + 7x + 49/4  49/4
=(x+7/2)^2  49/4
I added and subtracted the same number to maintain the "equality"
I assume you are learning the method of completing the square.
i am lost?
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