Question 211437
2. 16xy + 32yz – 20xyz
All terms are even numbers and have a y
4y*(4x + 8z - 5xz)
That's all that can be done.
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3. 9x2 – 64
Any difference of 2 squares is a plus and minus situation
(3x + 8)*(3x - 8)
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4. 5x3 – 125u2x
Factor out the 5x
= 5x*(x^2 - 25u^2)
Then there's difference to 2 squares
= 5x*(x - 5u)*(x + 5u)
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5. x2 + 7x + 12 
For this one, look for factors of 12 that add to 7.
12 = 1*12 --> 13 NG
12 = 2*6 --> 8 NG
12 = 3*4 -- 7 That's it
= (x+3)*(x+4)