帮我算算这几题,一:(-x²)³-3x²(x⁴+2x-x)二:2(x-2)
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帮我算算这几题,
一:(-x²)³-3x²(x⁴+2x-x)
二:2(x-2)²-(x+2)²(x-3)
三:求[(a+b)²-(a-b)²-8a³b²]÷(4ab)的值,其中a=1,b=2
一:(-x²)³-3x²(x⁴+2x-x)
二:2(x-2)²-(x+2)²(x-3)
三:求[(a+b)²-(a-b)²-8a³b²]÷(4ab)的值,其中a=1,b=2
![帮我算算这几题,一:(-x²)³-3x²(x⁴+2x-x)二:2(x-2)](/uploads/image/z/18335980-28-0.jpg?t=%E5%B8%AE%E6%88%91%E7%AE%97%E7%AE%97%E8%BF%99%E5%87%A0%E9%A2%98%2C%E4%B8%80%EF%BC%9A%EF%BC%88-x%26%23178%3B%29%26%23179%3B%EF%BC%8D3x%26%23178%3B%28x%26%238308%3B%EF%BC%8B2x%EF%BC%8Dx%29%E4%BA%8C%EF%BC%9A2%EF%BC%88x%EF%BC%8D2%EF%BC%89%26%23)
一.-x6:(-x²)³-3x²(x⁴+2x-x)
=-x6 -3x6-6x3+3x3
=-2x6-3x3
二:2(x-2)²-(x+2)²(x-3)
=2x2-8x+8-(x2+4x+4)(x-3)
=2x2-8x+8-x3-4x2-4x+3x2+12x+12
=-x3+x2+20
三:求[(a+b)²-(a-b)²-8a³b²]÷(4ab)的值,其中a=1, b=2
=(a2+2ab+b2-a2+2ab-b2-8a3b2) ÷(4ab)
=(4ab-8 a3b2) ÷(4ab)
=1-2a2b
把a=1,b=2代入
=1-2*2
=-3
=-x6 -3x6-6x3+3x3
=-2x6-3x3
二:2(x-2)²-(x+2)²(x-3)
=2x2-8x+8-(x2+4x+4)(x-3)
=2x2-8x+8-x3-4x2-4x+3x2+12x+12
=-x3+x2+20
三:求[(a+b)²-(a-b)²-8a³b²]÷(4ab)的值,其中a=1, b=2
=(a2+2ab+b2-a2+2ab-b2-8a3b2) ÷(4ab)
=(4ab-8 a3b2) ÷(4ab)
=1-2a2b
把a=1,b=2代入
=1-2*2
=-3
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