# How do you solve for s? (12x5 - 30x4) - (sx3 - 7)(2x2 - 5x + 3)

#### happiness

##### Junior Member
A polynomial expression is shown below.
(12x5 - 30x4) - (sx3 - 7)(2x2 - 5x + 3)
The expression is simplified to -18x3 + 14x2 - 35x + 21.

What is the value of s?

#### tkhunny

##### Moderator
Staff member
Have you considered multiplication?

#### happiness

##### Junior Member
Have you considered multiplication?
I didnt post the problem right, thanks for posting though. I'll have to make another post.

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#### stapel

##### Super Moderator
Staff member
A polynomial expression is shown below:

. . . . .(12x5 - 30x4) - (sx3 - 7)(2x2 - 5x + 3)

The expression is simplified to:

. . . . .-18x3 + 14x2 - 35x + 21

What is the value of s?
As suggested earlier, the first step will be to multiply out and simplify the given expression. Then you'll want to "equate coefficients". That is, you'll find the term in the first expression that has "s" in its coefficient, and you'll look at the corresponding term in the given simplified form. Since the polynomials can be equal only if their coefficients are the same, then you can equate the two relevant coefficients, and solve for the value of "s".

#### happiness

##### Junior Member

As suggested earlier, the first step will be to multiply out and simplify the given expression. Then you'll want to "equate coefficients". That is, you'll find the term in the first expression that has "s" in its coefficient, and you'll look at the corresponding term in the given simplified form. Since the polynomials can be equal only if their coefficients are the same, then you can equate the two relevant coefficients, and solve for the value of "s".
Can you show me step-by-step how you would do that? btw the problem is a picture attachment.

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#### stapel

##### Super Moderator
Staff member
Can you show me step-by-step how you would do that? btw the problem is a picture attachment.
You already have loads of step-by-step worked solutions in your book and in your class notes, so us doing this exercise for you isn't likely to make much difference. Now is the time to try something!

First, you need to multiply out the original expression. Where are you getting stuck in that process? (here) Please reply showing all of your steps so far. Thank you!

By the way, the attachment is way too small to be legible. Sorry.