SOLUTION: Im learning about factoring Trinomials by grouping and there is one problem I am having some trouble with. its 4r2(the 2 is the exponent) + 3r - 10

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Question 33617This question is from textbook Introductory Algebra
: Im learning about factoring Trinomials by grouping and there is one problem I am having some trouble with. its 4r2(the 2 is the exponent) + 3r - 10 This question is from textbook Introductory Algebra

Found 2 solutions by Nate, elima:
Answer by Nate(3500) About Me  (Show Source):
You can put this solution on YOUR website!
use this expression the help you greatly: ar^2 + br + c
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4r2(the 2 is the exponent) + 3r - 10
4r^2 + 3r -10 find factors of ac that add up to b
so............. ac in this problem is -40; know, find factors of -40 that adds up to 3........ the two factors are 8,-5
4r^2 + 8r - 5r - 10 use the two factors as r
(4r^2 + 8r) + (-5r - 10) group the problem
4r(r + 2) - 5(r + 2) take out the common factors
(4r - 5)(r + 2) your answer

Answer by elima(1433) About Me  (Show Source):
You can put this solution on YOUR website!
4r%5E2+3r-10
First of all you kno you are going to have a + and a - in the parenthesis;
(_ + _ )(_ - _)
Now you need to list your factors of 4;
1,4; 2;2
List factors of 10;
10,1; 2;5
Now you need to figure out which of these work; to do that;
lwts look at 1,4 and 2,5;
we multiply; 1*2 and 4*5; then add the answers;
2-20=-18 so we know that is wrong;
lets look at;
1*5=5
4*2=8, this may work;
Now by looking at the original trinomial e know the larger number is going to be +, because there is a +3;
(r+2)(4r-5)
I know this is hard to understand just by trying to read my explanation. I hope this helps some. If you have more questions e-mail me.
=)