SOLUTION: please help factor each trinomial 49z^2-42z+9 the answer is (7z-3)^2 how in the world do they come up with that?

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Question 65032: please help
factor each trinomial
49z^2-42z+9 the answer is (7z-3)^2 how in the world do they come up with that?

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
49z^2-42z+9 the answer is (7z-3)^2 how in the world do they come up with that?
49z^2-42a+9 is a perfect trinomial square
The 1st and 3rd terms are perfect squares
The 2nd term is -2 times the product of the square roots of the 1st and 3rd terms.
The factors are:
(7z-3)(7z-3) or (7z-3)^2
To see that this is true use FOIL to multiply (7z-3)(7z-3)
Cheers,
Stan H.