Polynomial long division: Linear divisor? HELP!?

(20x^3 – 9x^2 + 18x + 12) / (4x+3)

The first term in the quotient is 20x^3 / 4x = 5x^2. The result so far is 5x^2 + …

That 5x^2 multiplies by 3 to give 15x^2.

You therefore need to get -24x^2 from the next term multiplied by 4x. That makes it -6x, and the result becomes:

5x^2 – 6x + …

The -6x, on multiplication by 3 gives -18x, but you want 18x, and therefore need another 36x from multiplying the next term by 4x. That makes it 9. Result so far:

5x^2 – 6x + 9

The 9 multiplies by 3 to yield 27, and not 12.

The division therefore leaves a remainder of -15.

This website allows you to put in a problem and then they explain step by step how they did it. I am not a math major and could do this about 10 years ago… geesh that sounds bad but I am only 25!

Website I found for help: http://www.webmath.com/polymult.html

ooooooo….5x^2….-6x…+9 Remainder (-15)

………… ____________________

(4x+3) / (20x^3 – 9x^2 + 18x + 12)

…………..-20x^3 -15x^2 because you subtract -(20x^2 + 15x^2)

…………..———————

oooooooo……..-24x^2 + 18x

oooooooo…….+24x^2 +18x

oooooooo……..——————–

oooooooooooooo……..+36x + 12

oooooooooooooo………-36x + -27

oooooooooooooooooo—————

oooooooooooooooooooo……-15