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  • 1.(x-3y)(x+3y)-(x-3y)^2 2.98^2 3.(2x-y-3)(2x+y+3) 4.50.1^2 5.(5x+7y)^2-(5x-7y)^2

    1.(x-3y)(x+3y)-(x-3y)^2 2.98^2 3.(2x-y-3)(2x+y+3) 4.50.1^2 5.(5x+7y)^2-(5x-7y)^2
    注意^后面是平方,用平方差公式計(jì)算
    數(shù)學(xué)人氣:250 ℃時(shí)間:2020-04-05 04:33:09
    優(yōu)質(zhì)解答
    1.(x-3y)(x+3y)-(x-3y)^2
    =(x-3y)[(x+3y)-(x-3y)]
    =6y(x-3y)
    2.98^2
    =(100-2)^2
    =100^2-2x100x2+2^2
    =10000-400+4
    =99604
    3.(2x-y-3)(2x+y+3)
    =(2x)^2-(y+3)^2
    =4x^2-y^2-6y-9
    4.50.1^2
    =(50+0.1)^2
    =50^2+2x50x0.1+0.1^2
    =2500+10+0.01
    =2510.01
    5.(5x+7y)^2-(5x-7y)^2
    =[(5x+7y)+(5x-7y)][(5x+7y)-(5x-7y)]
    =140xy
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