SOLUTION: Can someone help me! I keep getting two different answers to this problem (3a^3+4a^2-a-1)(a-5) My two answers are 3a^4-15a^3+4a^3-21a^2+4a+5 and 3a^4-11a^3-21a^2+4a+5 I wa

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Can someone help me! I keep getting two different answers to this problem (3a^3+4a^2-a-1)(a-5) My two answers are 3a^4-15a^3+4a^3-21a^2+4a+5 and 3a^4-11a^3-21a^2+4a+5 I wa      Log On


   

Question 253266: Can someone help me! I keep getting two different answers to this problem (3a^3+4a^2-a-1)(a-5) My two answers are 3a^4-15a^3+4a^3-21a^2+4a+5 and 3a^4-11a^3-21a^2+4a+5 I want to lean more towards the bottom answer but I've used the calulater to a problem and it gave me the top answer.
Found 3 solutions by jim_thompson5910, Greenfinch, JimboP1977:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
%283a%5E3%2B4a%5E2-a-1%29%28a-5%29 Start with the given expression.


%28a-5%29%283a%5E3%2B4a%5E2-a-1%29 Rearrange the terms.


a%283a%5E3%2B4a%5E2-a-1%29-5%283a%5E3%2B4a%5E2-a-1%29 Expand. Recall that %28A%2BB%29%28C%2BD%2BE%2BF%29=A%28C%2BD%2BE%2BF%29%2BB%28C%2BD%2BE%2BF%29


Distribute.


3a%5E4%2B4a%5E3-a%5E2-a-15a%5E3-20a%5E2%2B5a%2B5 Multiply.


3a%5E4-11a%5E3-21a%5E2%2B4a%2B5 Now combine like terms.


So %283a%5E3%2B4a%5E2-a-1%29%28a-5%29 expands to 3a%5E4-11a%5E3-21a%5E2%2B4a%2B5.


In other words, %283a%5E3%2B4a%5E2-a-1%29%28a-5%29=3a%5E4-11a%5E3-21a%5E2%2B4a%2B5.


As verification, you can graph the two expressions and you'll see that they are indeed the same graph.

Answer by Greenfinch(383) About Me  (Show Source):
You can put this solution on YOUR website!
I agree the second answer is right.
multiply by a and you get 3a^4 + 4a^3 - a^2 - a
multiply by (-5) and you get -15 a^3 - 20 a^2 + 5a + 5
giving 3a^4 + (4-15)a^3 -(20 + 1)a^2 + (5 - 1)a +5

Answer by JimboP1977(311) About Me  (Show Source):