先化简再求值:4a²-3[a+4(1-a)-a²]-2(4a²-1),其中a=210x-[2x+(7x-3)-5] -4(5x-y)+3(-1/3x+4/3y+1)
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![先化简再求值:4a²-3[a+4(1-a)-a²]-2(4a²-1),其中a=210x-[2x+(7x-3)-5] -4(5x-y)+3(-1/3x+4/3y+1)](/uploads/image/z/1788710-14-0.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A4a%26%23178%3B-3%5Ba%2B4%EF%BC%881-a%EF%BC%89-a%26%23178%3B%5D-2%EF%BC%884a%26%23178%3B-1%EF%BC%89%2C%E5%85%B6%E4%B8%ADa%3D210x-%5B2x%2B%287x-3%29-5%5D+-4%285x-y%29%2B3%28-1%2F3x%2B4%2F3y%2B1%29)
先化简再求值:4a²-3[a+4(1-a)-a²]-2(4a²-1),其中a=210x-[2x+(7x-3)-5] -4(5x-y)+3(-1/3x+4/3y+1)
先化简再求值:4a²-3[a+4(1-a)-a²]-2(4a²-1),其中a=2
10x-[2x+(7x-3)-5] -4(5x-y)+3(-1/3x+4/3y+1)
先化简再求值:4a²-3[a+4(1-a)-a²]-2(4a²-1),其中a=210x-[2x+(7x-3)-5] -4(5x-y)+3(-1/3x+4/3y+1)
解1题
原式=4a²-3[a+4(1-a)-a²]-2(4a²-1)
=4a²-3(a+4-4a-a²)-8a²+2
=4a²-3a-12+12a+3a²-8a²+2
=(4a²+3a²-8a²)+(-3a+12a)+(-12+2)
=-a²+9a-10
当a=2时
原式=-2²+9×2-10
=-4+18-10
=18-14
=4
解2题
原式=10x-[2x+(7x-3)-5]
=10x-(2x+7x-3-5)
=10x-2x-7x+3+5
=(10x-2x-7x)+8
=x+8
解3题
原式=-4(5x-y)+3(-1/3x+4/3y+1)
=-20x+4y-x+4y+3
=(-20x-x)+(4y+4y)+3
=-21x+8y+3
4
4