The correct option is A 10x3−3x2+17xy+8y2+29x
Sum of first two expressions is
x3+x2−7xy+2y2+56x
−6x3+9x2−24xy+0y2−79x
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−5x3+10x2−31xy+2y2−23x---(1)
Sum of last two expressions,
5x3+0x2+2xy+4y2+0x
0x3+7x2−16xy+6y2+6x
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5x3+7x2−14xy+10y2+6x------(2)
Subtract equation (1) from (2),
5x3+7x2−14xy+10y2+6x
−5x3+10x2−31xy+2y2−23x
(+) (-) (+) (-) (+)
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10x3−3x2+17xy+8y2+29x