求已知A=x的2次方+xy+y的2次方,B=-2xy,则3A-4B=

2025-01-03 21:16:12
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回答1:

3A-4B
=3(x²+xy+y²)-4(-2xy)
=3x²+3xy+3y²+8xy
=3x²+11xy+3y²