Question 324715
Factor the trinomial 
s^2-9s+18
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Think of two numbers whose 
product = 18 
sum = -9
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The numbers are -6 and -3
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Substitute for the middle term of the quadratic to get:
s^2 - 6s-3s + 18
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Factor by groups:
s(s-6)-3(s-6)
Factor Again to get the final answer:
(s-6)(s-3)
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Cheers,
Stan H.
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