1.数学计算题 2.先化简,再求值.
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1.数学计算题 2.先化简,再求值.
1.(x+2)(x²+4)(x-2) 2.(x²y²-4)(-x²y²-4)-4(xy-1/2)乘(xy-1/2),其中x=1,y=-2.
1.(x+2)(x²+4)(x-2) 2.(x²y²-4)(-x²y²-4)-4(xy-1/2)乘(xy-1/2),其中x=1,y=-2.
(x+2)(x²+4)(x-2) =(x+2)(x-2) (x²+4) =(x²-4)(x²+4)=x⁴-16 2.(x²y²-4)(-x²y²-4)-4(xy-1/2)乘(xy-1/2),其中x=1,y=-2(x²y²-4)(-x²y²-4)-4(xy-1/2)·(xy-1\2),
=-[(xy)²-4²]-4(xy-1/2)²
=-[(-2)²-4²]-4(-2-1/2)²
=-(4-16)-4*(5/2)²
=12-4*25/4
=12-25
=-13
=-[(xy)²-4²]-4(xy-1/2)²
=-[(-2)²-4²]-4(-2-1/2)²
=-(4-16)-4*(5/2)²
=12-4*25/4
=12-25
=-13