Đáp án: a, A(x)=3x²-5x+x³-x²-7
=5x+2x²+x³-7
= x³+2x²+5x-7
B(x)=-5x+11+x³
= x³-5x+11
b,A(2)=3×2²-5×2+2³-2²-7
=12-10+8-4-7
=-1
B(-1)=(-1)³-5×(-1)+11
=15
c, (x³+2x²+5x-7)+(x³-5x+11)
=x³+2x²+5x-7+x³-5x+11
=2x³+2x²+4
=2(x³+2x²+2)
d,(x³+2x²+5x-7)-(x³-5x+11)
=x³+2x²+5x-7-x³+5x-11
=2x²+10x-18
=2(x²+5x-9)
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