SOLUTION: If {{{a-b=-6}}} and {{{b+c=9}}}, find the value of {{{3a^2-b^2-2c^2}}}.

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Question 1199499: If and , find the value of .
Answer by ikleyn(52803)   (Show Source): You can put this solution on YOUR website!
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If a-b = -6 and b+c = 9, find the value of .
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Then a = -6 + b,  c = 9 - b,


      3a^2 - b^2 - 2c^2 = 3*(-6+b)^2 - b^2 - 2*(9-b)^2 = 

    = 3*(36 - 12b + b^2) - b^2 - 2*(81 - 18b + b^2) = 108 - 36b + 3b^2 - b^2 - 162 + 36b - 2b^2 =

    = combine like terms = -54. 


ANSWER.  If a-b = -6  and  b+c = 9, then the value of  is -54.

Solved.



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