Hi everyone, first post here

i'd appreciate it if anyone could help me with this question.

If (x-2A)(2x+1)=2x^{2}-Bx+10, then A • B =

thanks a lot

if this is in the wrong subforum sorry, its precalc homework so i put it here

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- Aug 31st 2013, 11:39 PMHell0Homework question
Hi everyone, first post here

i'd appreciate it if anyone could help me with this question.

If (x-2A)(2x+1)=2x^{2}-Bx+10, then A • B =

thanks a lot

if this is in the wrong subforum sorry, its precalc homework so i put it here - Sep 1st 2013, 02:47 AMchiroRe: Homework question
Hey Hell0.

Hint: Try expanding both sides and multiply both sides by A so that you can match up the AB term and use the rest of the variables to solve for A,B (remember that in a quadratic, you have fx^2 + gx + c with three constants f,g,c). - Sep 1st 2013, 09:40 AMHell0Re: Homework question
Hi. this is what i tried

x - 4Ax = -Bx

and

-2A = 10

found a:

A = -5

then plugged it in:

x - 4(-5)x = -Bx

x + 20x = -Bx

pulled out the x because they all have it:

x + 20x = -Bx

1 + 20 = -B

-B = 21

B = -21

-21 * -5 = 105

The answer is 105? - Sep 1st 2013, 08:57 PMibduttRe: Homework question
( x- 2A )( 2x + 1 ) = 2x^2-Bx +10

2x^2 +x - 4Ax - 2A = 2x^2-Bx +10

2x^2 + ( 1 - 4A ) x - 2A = 2x^2-Bx +10

Now compare the coefficients and conclude.

You will get A*B = 105 - Sep 1st 2013, 09:39 PMHell0Re: Homework question
hey thanks everyone. can you try to help me with this one? http://mathhelpforum.com/pre-calculu...-question.html its the only blank question i have left. id really appreciate it

- Sep 2nd 2013, 04:37 PMHell0Re: Homework question
*solved*