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Question
In the expansion of (2x2 - 8) (x - 4)2; find the value of coefficient of x3.
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Solution
( 2x2 - 8 )( x - 4 )2
= ( 2x2 - 8 )( x2 - 8x + 16 )
= 2x2( x2 - 8x + 16 ) - 8( x2 - 8x + 16 )
= 2x4 - 16x3 + 32x2 - 8x2 + 64x -128
= 2x4 - 16x3 + 24x2 + 64x - 128
Hence,
Coefficient of x3 = - 16
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