Mathematics
Expand : (2x - y + 2)3
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Answer
Given: (2x - y + 2)3
= (2x - y + 2)2 (2x - y + 2)
Using the formula: (a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca
= [(2x)2 + (-y)2 + (2)2 + 2 2x (-y) + 2 (-y) 2 + 2 2 2x] (2x - y + 2)
= [4x2 + y2 + 4 - 4xy - 4y + 8x] (2x - y + 2)
= 4x2 (2x - y + 2) + y2 (2x - y + 2) + 4 (2x - y + 2) - 4xy (2x - y + 2) - 4y (2x - y + 2) + 8x (2x - y + 2)
= 8x3 - 4x2y + 8x2 + 2xy2 - y3 + 2y2 + 8x - 4y + 8 - 8x2y + 4xy2 - 8xy - 8xy + 4y2 - 8y + 16x2 - 8xy + 16x
= 8x3 - y3 + 8 - 12x2y + 24x2 + 6xy2 + 6y2 + 24x - 12y -24xy
Hence, (2x - y + 2)3 = 8x3 - y3 + 8 - 12x2y + 24x2 + 6xy2 + 6y2 + 24x - 12y -24xy.
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