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January 31, 2015

January 31, 2015

Posted by **Mimi** on Tuesday, May 3, 2011 at 5:34pm.

(9t² - t- 7)(4t²+9t-1)

AND

Find the product.

(5a+2)³

- Math -
**MathMate**, Tuesday, May 3, 2011 at 9:36pmMultiply:

(9t² - t- 7)(4t²+9t-1)

You can do a long multiplication, with the appropriate terms in the same columns, just like the multiplication of multi-digit numbers.

Alternatively, you can multiply visually, looking for highest to lowest terms:

t^4: 9*4 =36

t^3: 9*9+4(-1)=77

t^2: 9(-1)+(-1)(9)+(-7)(4)=-46

t: (-7)(9)+(-1)(-1)=-62

1: (-7)(-1) = 7

So the product is:

36t^4+77t^3-46t^2-62t+7

Quick check:

put t=1, so calculate the sum of coefficients of each factor:

(9t² - t- 7)(4t²+9t-1)

=(9-1-7)(4+9-1)

=1*12

=12

Sum of coefficients of product

=36+77-46-62+7

=12

checks.

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