1.已知A=2xy-2²+8x²,B=9x²+3xy-5y²,求(1)A-B(2)-3A+2B的值先化简,在求值.2.(2x²+x)-[4x²-(3²-x)],其中x=2/33.1/2m-2(m-1/3n²)-(3/2m-1/3n²),其中m=1/3,n=-1.
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![1.已知A=2xy-2²+8x²,B=9x²+3xy-5y²,求(1)A-B(2)-3A+2B的值先化简,在求值.2.(2x²+x)-[4x²-(3²-x)],其中x=2/33.1/2m-2(m-1/3n²)-(3/2m-1/3n²),其中m=1/3,n=-1.](/uploads/image/z/2666342-38-2.jpg?t=1.%E5%B7%B2%E7%9F%A5A%3D2xy-2%26%23178%3B%2B8x%26%23178%3B%2CB%3D9x%26%23178%3B%2B3xy-5y%26%23178%3B%2C%E6%B1%82%EF%BC%881%EF%BC%89A-B%EF%BC%882%EF%BC%89-3A%2B2B%E7%9A%84%E5%80%BC%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%9C%A8%E6%B1%82%E5%80%BC.2.%EF%BC%882x%26%23178%3B%2Bx%EF%BC%89-%5B4x%26%23178%3B-%283%26%23178%3B-x%29%5D%2C%E5%85%B6%E4%B8%ADx%3D2%2F33.1%2F2m-2%28m-1%2F3n%26%23178%3B%29-%283%2F2m-1%2F3n%26%23178%3B%29%2C%E5%85%B6%E4%B8%ADm%3D1%2F3%2Cn%3D-1.)
1.已知A=2xy-2²+8x²,B=9x²+3xy-5y²,求(1)A-B(2)-3A+2B的值先化简,在求值.2.(2x²+x)-[4x²-(3²-x)],其中x=2/33.1/2m-2(m-1/3n²)-(3/2m-1/3n²),其中m=1/3,n=-1.
1.已知A=2xy-2²+8x²,B=9x²+3xy-5y²,求(1)A-B(2)-3A+2B的值
先化简,在求值.
2.(2x²+x)-[4x²-(3²-x)],其中x=2/3
3.1/2m
-2(m-1/3n²)-(3/2m-1/3n²),其中m=1/3,n=-1.
1.已知A=2xy-2²+8x²,B=9x²+3xy-5y²,求(1)A-B(2)-3A+2B的值先化简,在求值.2.(2x²+x)-[4x²-(3²-x)],其中x=2/33.1/2m-2(m-1/3n²)-(3/2m-1/3n²),其中m=1/3,n=-1.
已知A=2xy-2²+8x²,B=9x²+3xy-5y²,
(1)A-B
=2xy-2y²+8x²-9x²-3xy+5y²
=-x²+3y²-xy;
(2)-3A+2B
=-3(2xy-2y²+8x²)+2(9x²+3xy-5y²)
=-6xy+6y²-24x²+18x²+6xy-10y²
=-6x²-4y²;
2.(2x²+x)-[4x²-(3²-x)],其中x=2/3
=2x²+x-4x²+9-x
=-2x²+9
=-2×4/9+9
=-8/9+9
=73/9;
3.1/2m-2(m-1/3n²)-(3/2m-1/3n²),其中m=1/3,n=-1.
=m/2-2m+2n²/3-3m/2+n²/3
=-3m+n²
=-3×1/3+(-1)²
=-1+1
=0;
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