Checking my work

**NotThatGood** · August 26th 2009, 07:02 AM

Multiply
(8x+4)(8x^2+2x+8)
My work;
8x^2 +2x +8
8x+4
32x^2+8x + 32
64x^2+16x^2+64x
64x^2+48x^2+72x+32
112x^2+72x+32
Have I done a good job?

**mathaddict** · August 26th 2009, 07:08 AM

Originally Posted by NotThatGood

Multiply
(8x+4)(8x^2+2x+8)
My work;
8x^2 +2x +8
8x+4
32x^2+8x + 32
64x^2+16x^2+64x
64x^2+48x^2+72x+32
112x^2+72x+32
Have I done a good job?

$(8x+4)(8x^2+2x+8)$

$=64x^3+16x^2+64x+32x^2+8x+32$

$=64x^3=48x^2+72x+32$

**HallsofIvy** · August 26th 2009, 07:22 AM

Originally Posted by mathaddict

$(8x+4)(8x^2+2x+8)$

$=64x^3+16x^2+64x+32x^2+8x+32$

$=64x^3=48x^2+72x+32$

typo:
$=64x^3$ + $48x^2+72x+32$
of course.

**HallsofIvy** · August 26th 2009, 07:25 AM

Originally Posted by NotThatGood

Multiply
(8x+4)(8x^2+2x+8)
My work;
8x^2 +2x +8
8x+4
32x^2+8x + 32
64x^2+16x^2+64x
64x^2+48x^2+72x+32

8x^2 times 8x is 64x^3, not 64x^2.

112x^2+72x+32
Have I done a good job?

Thread: Checking my work