先化简再求值:5(2a-b)-2(6a-2b+2)+4(a-3\4b-1\8),a=2\3,b=-5\3.
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先化简再求值:5(2a-b)-2(6a-2b+2)+4(a-3\4b-1\8),a=2\3,b=-5\3.
先化简再求值:5(2a-b)-2(6a-2b+2)+4(a-3\4b-1\8),a=2\3,b=-5\3.
先化简再求值:5(2a-b)-2(6a-2b+2)+4(a-3\4b-1\8),a=2\3,b=-5\3.
5(2a-b)-2(6a-2b+2)+4(a-3\4b-1\8)
=10a-5b-12a+4b-4+4a-3b-1/2
=2a-4b-9/2
=1/2(4a-8b-9)
再将a=2\3,b=-5\3.代入
原式=1/2(4a-8b-9)
=1/2(4×2/3+8×5/3-9)
=3·5
原式=10a-5b-12a+4b-4+4a-3b-1/2
=2a-4b-9/2
=2*2/3+4*5/3-9/2
=7/2