一、先化简,再求值:3x³-【x³+(6x²-7x)】-2(x³-3x²-4x),其中,x=-1二、化简:(1)3x+2x²-2-15x²+1-5x(2)3x²+2xy-4y²-3xy+4y²-3x²(3)-7x²+(6x²-5xy)-2(3y&
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![一、先化简,再求值:3x³-【x³+(6x²-7x)】-2(x³-3x²-4x),其中,x=-1二、化简:(1)3x+2x²-2-15x²+1-5x(2)3x²+2xy-4y²-3xy+4y²-3x²(3)-7x²+(6x²-5xy)-2(3y&](/uploads/image/z/447884-44-4.jpg?t=%E4%B8%80%E3%80%81%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A3x%26%23179%3B-%E3%80%90x%26%23179%3B%2B%EF%BC%886x%26%23178%3B-7x%EF%BC%89%E3%80%91-2%EF%BC%88x%26%23179%3B-3x%26%23178%3B-4x%EF%BC%89%2C%E5%85%B6%E4%B8%AD%2Cx%3D-1%E4%BA%8C%E3%80%81%E5%8C%96%E7%AE%80%EF%BC%9A%EF%BC%881%EF%BC%893x%2B2x%26%23178%3B-2-15x%26%23178%3B%2B1-5x%EF%BC%882%EF%BC%893x%26%23178%3B%2B2xy-4y%26%23178%3B-3xy%2B4y%26%23178%3B-3x%26%23178%3B%EF%BC%883%EF%BC%89-7x%26%23178%3B%2B%EF%BC%886x%26%23178%3B-5xy%EF%BC%89-2%EF%BC%883y%26)
一、先化简,再求值:3x³-【x³+(6x²-7x)】-2(x³-3x²-4x),其中,x=-1二、化简:(1)3x+2x²-2-15x²+1-5x(2)3x²+2xy-4y²-3xy+4y²-3x²(3)-7x²+(6x²-5xy)-2(3y&
一、
先化简,再求值:
3x³-【x³+(6x²-7x)】-2(x³-3x²-4x),其中,x=-1
二、化简:
(1)3x+2x²-2-15x²+1-5x
(2)3x²+2xy-4y²-3xy+4y²-3x²
(3)-7x²+(6x²-5xy)-2(3y²+xy-x²)
(4)2(2x²-5x)-5(3x+5-2x²)
一、先化简,再求值:3x³-【x³+(6x²-7x)】-2(x³-3x²-4x),其中,x=-1二、化简:(1)3x+2x²-2-15x²+1-5x(2)3x²+2xy-4y²-3xy+4y²-3x²(3)-7x²+(6x²-5xy)-2(3y&
1.3x³-x³-6x²+7x-2x³+6x²+8x
=15x
∵x=1
∴15x=15×1=15
2.(1)3x+2x²-2-15x²+1-5x
=-2x-13x²-1
(2)3x²+2xy-4y²-3xy+4y²-3x²
=-xy
(3)-7x²+(6x²-5xy)-2(3y²+xy-x²)
=-7x²+6x²-5xy-6y²-2xy+2x²
=x²-7xy-6y
(4)2(2x²-5x)-5(3x+5-2x²)
=4x²-10x-15x-25+10x²
=14x²-25x-25
第一题:
3x³-【x³+(6x²-7x)】-2(x³-3x²-4x)
=3x³-x³-6x²+7x-2x³+6x²+8x
=15x
=-15
第二题:
(1)3x+2x²-2-15x²+1-5x
=-1...
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第一题:
3x³-【x³+(6x²-7x)】-2(x³-3x²-4x)
=3x³-x³-6x²+7x-2x³+6x²+8x
=15x
=-15
第二题:
(1)3x+2x²-2-15x²+1-5x
=-13x²-2x-1
化简到什么地步啊?我好多年不做数学题了,忘得差不多了
(2)3x²+2xy-4y²-3xy+4y²-3x²
=-xy
(3)-7x²+(6x²-5xy)-2(3y²+xy-x²)
=-7x²+6x²-5xy-6y²-2xy+2x²
=x²-7xy-6y²
(4)2(2x²-5x)-5(3x+5-2x²)
=4x²-10x-15x-25+10x²
=14x²-25x-25
收起