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Math

posted by .

Mutliply.

(9t² - t- 7)(4t²+9t-1)

AND

Find the product.

(5a+2)³

  • Math -

    Multiply:
    (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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