Wanted: Algebra Expert.... How Does This Make Sense???

Question

150-5v-5v^2

First I put in descending order
-5v^2-5v+150

I then take out the common factor which in this case is (-5) and change my signs.

-5(v^2+v-30)

Then, Multiply 1(-30) which is (-30). I move on to find factors of (-30) that when added also give me the sum of 1v.

My answer is 5(-6).

Then I place them into my problem and factor by grouping....

(v^2+5v-6v-30)... and that yields v(v+5)-6(v+5)

When combined this is (v-6)(v+5)... and since there was a common factor that needed to be taken out in the beginning I also have to add that in to finally get my answer of...

5(v-6)(v+5)

My MathLab that I have to use to submit my homework is tell me that my signs are wrong and that the answer is 5(5-v)(6+v).

Why is this and what difference does it make?? I did all the steps as I was taught. Explain please.

Answer 1

"Then I place them into my problem and factor by grouping....

(v^2+5v-6v-30)... and that yields v(v+5)-6(v+5) "

... wait, it should be (v^2-5v+6v-30) because the middle sign is positive. That's where you erred.

If the roots are 5 & -6, (although you said it was your answer)
then the factors are (v-5) (v+6)
(you probably chose the wrong number to choose from -30.)

d:

Answer 2

Wanted: Algebra Expert.... How Does This Make Sense???
150-5v-5v^2

First I put in descending order
-5v^2-5v+150

I then take out the common factor which in this case is (-5) and change my signs.

-5(v^2+v-30)

Then, Multiply 1(-30) which is (-30). I move on to find factors of (-30) that when added also give me the sum of 1v.

My answer is 5(-6).

You made the mistake here. That should be -5 and 6 when added give you + 1 - Swamy

Then I place them into my problem and factor by grouping....

(v^2+5v-6v-30)... and that yields v(v+5)-6(v+5)

That should be v + 6 and v - 5 - Swamy

When combined this is (v-6)(v+5)... and since there was a common factor that needed to be taken out in the beginning I also have to add that in to finally get my answer of...

5(v-6)(v+5)

That would be - 5 (v + 6) (v - 5)

My MathLab that I have to use to submit my homework is tell me that my signs are wrong and that the answer is 5(5-v)(6+v).

-5 (v + 6) ( v - 5) = 5 (5 - v) ( 6 + v)

Why is this and what difference does it make?? I did all the steps as I was taught. Explain please.

I hope you understood now.

Regards.

Swamy

Answer 3

Factor it back out both ways.

Your answer gives you -30 times 5 which is -150:
5(v-6)(v+5)
5(v^2 + 5v - 6v -30)
5(v^2 -1v - 30)
5v^2 - 5v - 150 The sign is wrong here you wanted + 150 and -5v^2.

Their answer:
5(5-v)(6+v) or 5(-v+5)(v+6) I will do it the first way since that is the way you have it written.
5(5-v)(6+v)
5(30 + 5v -6v - v^2) Notice the sign differences
5(30 - 1v - v^2)
150 - 5v - 5v^2 or -5v^2 -5v+150

So where you said:
Then, Multiply 1(-30) which is (-30). I move on to find factors of (-30) that when added also give me the sum of 1v.

My answer is 5(-6).

This is where your error occurred. Because:

When added, 5 and (-6) give -1
When added, (-5) and 6 give 1

You wanted -5 and 6 not the other.

Hope this explains it a little better for you.

Answer 4

Starting from -5v^2-5v+150, we factor out -5 and get
-5(v^2+v-30), or -5(v+6)(v-5).
If you want to bring the minus sign back into the parenthesis, you would get 5(v+6)(5-v), the minus sign must only be factored into one of the two factors. This result is the same as the one given in your book.

Answer 5

Your mistake is after this step:

-5(v^2+v-30)


If you want to factor that bracket, you need to find two numbers that add to +1 (hence the +v), and multiply to -30.

These numbers are (-5) and (6).

-5+6 = 1
-5*6= -30

So it should look like this

-5(v-5)(v+6)

If you want to get rid of the negative, then multiply both sides by negative 1. Remember this whole thing we're going to say is equal to 0.

=5(5+v)(6-v)

Answer 6

You lost a negative sign. Look at step 3, where you take out negative 5, and then in step 5 where you have 5(v-6)(v+5). There should be a negative sign in front of the 5 for -5(v-6)(v+5).

Answer 7

Then, Multiply 1(-30) which is (-30). I move on to find factors of (-30) that when added also give me the sum of 1v.

My answer is 5(-6).

When added, 5 and (-6) give -1
When added, (-5) and 6 give 1

Answer 8

It's because you have factors of 5 and -6, but you want them to sum to 1. 5 and -6 sum to -1.
That's why mathlab is telling you to switch the signs - so you have 6 and -5, which sum to 1.


___________________
Hope that helps, Adam
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Answer 9

It doesn't matter if you took out five or negative five. Just as long as the signs changed respectively in parentheses. The MathLab says its wrong because it has the correct answer stored only one way. A lot of older programs have this problem. What I would do is take it to the teacher and have them give you credit since you did yield the right answer.

Answer 10

I personally am having a very difficult time with the class, but it just really depends on the teacher you get. Some teachers like to take it really slow, which has good and bad outcomes. Others like to take it fast, like my teacher. If you get a teacher that likes to study some Hong new everyday like mine, your best bet would be to stay after school whenever possible for extra help on homework and such. Also, when possible, make corrections to papers with bad grades. Not only will it help you understand what you gto wrong, it will also help you not to miss it next time. If you use these tips, you should be able to manage, even if you don't get the "perfect A" :)