# Thread: similarity becomes an identity

1. ## similarity becomes an identity

Determine the constants A and B so that the similarity becomes an identity.

A(4-x)+3x=B(9+2x)

Some help would be great thanks!

2. ## Re: similarity becomes an identity

Originally Posted by sunnshine345
Determine the constants A and B so that the similarity becomes an identity.

A(4-x)+3x=B(9+2x)

Some help would be great thanks!
It would be nice of you to show of your work and tell us what you don't understand.
Otherwise, we are left guessing as to what you need.

3. ## Re: similarity becomes an identity

I really have no idea how to solve this

4. ## Re: similarity becomes an identity

Originally Posted by sunnshine345
Determine the constants A and B so that the similarity becomes an identity.

A(4-x)+3x=B(9+2x)

Some help would be great thanks!
no idea at all?

$4A -Ax + 3x = 9B + 2Bx$

for an identity this must hold true for all x. So equate the constant bits and equate the bits multiplying $x$.

$4A=9B$

$3-A=2B$

Do you understand this? If not stop and look at it until you do.

Now we have two equations and 2 unknowns and use your favorite method to solve this system of equations.

You should know how to do this so I'm going to leave it to you to finish.