SOLUTION: hi im doing my summer math hw and i dont understand factoring like this 5x squared plus 21x +4 ??????????????????????????????????????????? help me

Question 149166: hi im doing my summer math hw and i dont understand factoring like this 5x squared plus 21x +4 ??????????????????????????????????????????? help me
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
i dont understand factoring like this 5x squared plus 21x +4
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5x^2 + 21x + 4
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Use the AC Method.
Think of two numbers whose product is 4*5= 20
and whose sum is 21.
The numbers are 20 and 1.
-------------------
Replace the middle term wigh 20x + x:
5x^2 + 20x + x + 4
Factor the 1st two and the last two terms separately:
5x(x + 4) + (x+4)
Factor again to get:
(x+4)(5x+1)
==================================
Cheers,
Stan H.
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