Trinomial trouble

R

ryanbishop

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Joined
Nov 19, 2014
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4
Hi,

I'm doing review problems for a math course I'm taking on Finite Math. I'm having trouble with this problem:

x2 + 4x -5

According to my book, the answer is: (x+5)(x-1)

I'm not sure how it's getting that. This is my work:

x2 * -5= -5x2

Factors: -5x and 1x
5x and -1x (I use this because it equals 4x above)

Then: x2+5x -1x-5
(x2+5x)(-1x-5)

I get: x(x+5) -1(x-4)

This is wrong obviously but I don't understand how you get -1(x-5) in the second part to end up with a final answer of (x+5)(x-1).

Thanks for any help.
 
ryanbishop said:
I'm doing review problems for a math course I'm taking on Finite Math. I'm having trouble with this problem:

x2 + 4x -5
Click to expand...
Since you're reviewing, this means that your class has already covered this topic. You may find it helpful to go back and review that section or chapter in the book, along with your class notes from that week. Also helpful can be online lessons explaining and demonstrating how to factor quadratics.

ryanbishop said:
This is my work:

x2 * -5= -5x2
Click to expand...
How did the expression (something with no "equals" sign) become an equation (something with an "equals" sign)? :shock:

ryanbishop said:
Factors: -5x and 1x
Click to expand...
Of what are these "factors"?

Please note that you can solve an equation only by having the equation equal to zero. So, even if you had been given an equation and had been told to solve, this would not have led to a valid solution. In any case, you're being told to factor an expression, so there will be a much higher probability of success if you try a method that's designed for this sort of thing. ;)
 
I'm using the method found here and up until this problem I haven't had any issues. I know how to solve it basically throwing numbers out and seeing if they work but I was trying to use that method.

Thanks though.
 
Last edited:
ryanbishop said:
Hi,

I'm doing review problems for a math course I'm taking on Finite Math. I'm having trouble with this problem:

x2 + 4x -5

According to my book, the answer is: (x+5)(x-1)

I'm not sure how it's getting that. This is my work:

x2 * -5= -5x2

Factors: -5x and 1x
5x and -1x (I use this because it equals 4x above)

Then: x2+5x -1x-5
(x2+5x) + (-1x-5)

I get: x(x+5) -1(x-4) ..... that should be x(x+5) - 1(x +5) then to (x+5)(x-1)

This is wrong obviously but I don't understand how you get -1(x-5) in the second part to end up with a final answer of (x+5)(x-1).

Thanks for any help.
Click to expand...
.
 
ryanbishop said:
That's what I was guessing but wasn't sure. So, if I ever have something like (x-8) it can be converted to -1(x+8)? I think that's a rule I don't know because I would just assume it becomes -7.
Click to expand...

You do know that:

-1(x+8) ..... means ....... -1 * (x+8)

Then

-1(x+8) = -1 * (x+8) = (-1) * x + (-1) * 8 = -x + (-8) = -x - 8

If you don't - you need o review the rules of arithmetic operations.
 
Denis said:
...and LISTEN during math classes :idea:
Click to expand...


This site is called "FreeMathHelp" and this is the second demeaning and rude comment for a simple question. Maybe the site should be labeled "GoSomewhereElse" since the only help has been to go anywhere but here. I'm not coming here again. Hopefully you'll be helpful to someone in the future.
 
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