# Need help studying for my final... today (:

#### aem2177

##### New member
I have no clue how to factor, which seems to be a big chunk of what's going to be on my exam.

I have one problem done that I THINK I did right, but I'm not sure.

y(b+9)+5(b+9)
=(y+5)(b+9)

I don't know if that's right or not, but I remember my teacher saying something like "factor by grouping" and it looking similar to that.

I have a number of other problems from the study guide that I simply do not even know where to begin with. I'll list two.

1. z^2+7zy+5z+35y
2. 7x^2-70x+147

Any help on the steps to do these would be greatly appreciated!

#### masters

##### Full Member
aem2177 said:
I have no clue how to factor, which seems to be a big chunk of what's going to be on my exam.

I have one problem done that I THINK I did right, but I'm not sure.

y(b+9)+5(b+9)
=(y+5)(b+9)

I don't know if that's right or not, but I remember my teacher saying something like "factor by grouping" and it looking similar to that.

I have a number of other problems from the study guide that I simply do not even know where to begin with. I'll list two.

1. z^2+7zy+5z+35y
2. 7x^2-70x+147

Any help on the steps to do these would be greatly appreciated!
Hi aem2177,

You did fine with your grouping. Good job.

1. $$\displaystyle z^2+7zy+5z+35y$$

This one's already grouped. Factor z from the first group, and then factor 5 from the second group.

$$\displaystyle z(z+7y)+5(z+7y)$$

Now, finish up like you did the last one.

2. $$\displaystyle 7x^2-70x+147$$

Now, 7 is a factor of all three terms, so if we factor that out first, we have,

$$\displaystyle 7(x^2-10x+21)$$

Now, I think you can factor the trinomial in parentheses, can't you?

#### Subhotosh Khan

##### Super Moderator
Staff member
aem2177 said:
I have no clue how to factor, which seems to be a big chunk of what's going to be on my exam.

I have one problem done that I THINK I did right, but I'm not sure.

y(b+9)+5(b+9)
=(y+5)(b+9) <<< Correct

I don't know if that's right or not, but I remember my teacher saying something like "factor by grouping" and it looking similar to that.

I have a number of other problems from the study guide that I simply do not even know where to begin with. I'll list two.

1. z^2+7zy+5z+35y = (z^2 +7zy) + (5z + 35y) = (z * z +7 * z * y) + ( 5 * z + 7 * 5 * y) = z(z + 7) + 5(z + 7)
2. 7x^2-70x+147 <<< This is a quadratic equation. This needs different method - what have learned abot these

Any help on the steps to do these would be greatly appreciated!