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Jack rewrites the quadratic 9x^2 - 30x - 42 - x^2 - 2x in the form of (ax + b)^2 + c, where a, b, and c are all integers. What is ab?

 Oct 5, 2021
 #1
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9x^2 - 30x - 42 - x^2 - 2x  =

8x^2 - 32x - 42  = 0     

8 (x^2 - 4x)        - 42   = 0          'Complete the square'  for 'x'  

8 ( x-2)2    - 32    -42    = 0

8 (x-2)2 - 74   = 0                           <====== Now you can see a    b   and   c   to finish

 Oct 5, 2021

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