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幼苗
共回答了22个问题采纳率:95.5% 举报
1,
(2a+3)²-(a-2)(a+2)
=(4a^2+12a+9)-(a^2-4)
=3a^2+12a+13
2,3cd²分之3a²b乘21bd³分之8a²c²÷7a分之2c
(3a^2b)/(3cd^2)*(8a^2c^2)/(21bd^3)/2c/7a
=[(3a^2b)*(8a^2c^2)]/[(3cd^2)*(21bd^3)]*7a/2c
=(24a^4bc^2)/(63bcd^5)*7a/2c
=7a(24a^4bc^2)/[2c(63bcd^5]
=4a^5/(3d^5)
=4/3(a/d)^5
3.[(x+2y)(x-2y)-(x+4y)²]÷4y
=[(x^2-4y^2)-(x^2+8xy+16y^2)]/4y
=-(20y^2+8xy)/4y
=-(5y+2x)
1年前
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