(1):(x+2y)²-(x+y)(3x-y) (2):(2x+3y)²-(2x-3y)²
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(1):(x+2y)²-(x+y)(3x-y) (2):(2x+3y)²-(2x-3y)²
(3):2a(5a-2分之1b²)-3a(5a-b²) (4):(9x³y²-6xy+3xy²)÷(-3xy) (5):化简求值:(2x+y)²-(2x-y)(x+y)-2(x-2y)(x+2y),其中x+2分之1,y=2 (6):先化简(2x-1)²-(3x+1)(3x-1)+5x(x-1),再选取一个你喜欢的数代替x,并求原代数式的值 求求求!
(3):2a(5a-2分之1b²)-3a(5a-b²) (4):(9x³y²-6xy+3xy²)÷(-3xy) (5):化简求值:(2x+y)²-(2x-y)(x+y)-2(x-2y)(x+2y),其中x+2分之1,y=2 (6):先化简(2x-1)²-(3x+1)(3x-1)+5x(x-1),再选取一个你喜欢的数代替x,并求原代数式的值 求求求!
(1):(x+2y)²-(x+y)(3x-y)
=x²+4xy+4y²-3x²+xy-3xy+y²
=-2x²+2xy+5y²
(2):(2x+3y)²-(2x-3y)²
=(2x+3y+2x-3y)(2x+3y-2x+3y)
=4x*6y
=24xy
(3):2a(5a-2分之1b²)-3a(5a-b²)
=a(10a-b²-15a+3b²)
=a(2b²-5a)
=2ab²-5a²
(4):(9x³y²-6xy+3xy²)÷(-3xy)
=9x³y²/(-3xy)-6xy/(-3xy)+3xy²/(-3xy)
=-3x²y+2-y
(5):化简求值:(2x+y)²-(2x-y)(x+y)-2(x-2y)(x+2y),其中x=2分之1,y=2
(2x+y)²-(2x-y)(x+y)-2(x-2y)(x+2y)
=4x²+4xy+y²-(2x²+2xy-xy-y²)-(2x²+4xy-4xy-8y²)
=4x²+4xy+y²-2x²-xy+y²-2x²+8y²
=3xy+10y²
=3*1/2*2+10*2²
=3+40
=43
(6):先化简(2x-1)²-(3x+1)(3x-1)+5x(x-1),再选取一个你喜欢的数代替x,并求原代数式的值
(2x-1)²-(3x+1)(3x-1)+5x(x-1)
=(2x-1)²-(3x)²+1+5x²-5x
=(2x-1+3x)(2x-1-3x)+1+5x²-5x
=(5x-1)(-x-1)+1+5x²-5x
=-5x²-5x+x+1+1+5x²-5x
=-9x+2
假设x=8
原式=-9*8+2=-70
=x²+4xy+4y²-3x²+xy-3xy+y²
=-2x²+2xy+5y²
(2):(2x+3y)²-(2x-3y)²
=(2x+3y+2x-3y)(2x+3y-2x+3y)
=4x*6y
=24xy
(3):2a(5a-2分之1b²)-3a(5a-b²)
=a(10a-b²-15a+3b²)
=a(2b²-5a)
=2ab²-5a²
(4):(9x³y²-6xy+3xy²)÷(-3xy)
=9x³y²/(-3xy)-6xy/(-3xy)+3xy²/(-3xy)
=-3x²y+2-y
(5):化简求值:(2x+y)²-(2x-y)(x+y)-2(x-2y)(x+2y),其中x=2分之1,y=2
(2x+y)²-(2x-y)(x+y)-2(x-2y)(x+2y)
=4x²+4xy+y²-(2x²+2xy-xy-y²)-(2x²+4xy-4xy-8y²)
=4x²+4xy+y²-2x²-xy+y²-2x²+8y²
=3xy+10y²
=3*1/2*2+10*2²
=3+40
=43
(6):先化简(2x-1)²-(3x+1)(3x-1)+5x(x-1),再选取一个你喜欢的数代替x,并求原代数式的值
(2x-1)²-(3x+1)(3x-1)+5x(x-1)
=(2x-1)²-(3x)²+1+5x²-5x
=(2x-1+3x)(2x-1-3x)+1+5x²-5x
=(5x-1)(-x-1)+1+5x²-5x
=-5x²-5x+x+1+1+5x²-5x
=-9x+2
假设x=8
原式=-9*8+2=-70
先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y
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