Math
posted by John .
We are studying polynomials
(x+3)(x7)=0
2x^2+3x9=0
5x^2+2x=0

x =  3 or x = 7 makes the left zero.
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factors of 2 are 1 and 2
factors of 9 are 1, 9, 3
need combination that differs by 3
well 2 * 3 and 3 will work
(2 x  3) (x+3) = 0
x = 3/2 or x = 3 makes the left zero
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now really try them first yourself
x (5 x + 2) = 0
x = 0 or x = 2/5 makes it zero