已知实数mn满足m+1/2的绝对值与n^2-n+1/4互为相反数,化简并求值:(3m-2n)^2+(3m+2n)(3m-

已知实数mn满足m+1/2的绝对值与n^2-n+1/4互为相反数,化简并求值:(3m-2n)^2+(3m+2n)(3m-2n)-9(m+n)^2
可爱儿810923 1年前 已收到3个回答 举报

菁菁的柠檬草 幼苗

共回答了15个问题采纳率:100% 举报

∵m+1/2的绝对值非负数,n^2-n+1/4=(n-1/2)^2也非负数
又:m+1/2的绝对值与n^2-n+1/4互为相反数
∴m+1/2的绝对值=0,n^2-n+1/4=(n-1/2)^2=0
∴m=-1/2,n=1/2
∴m+n=0
(3m-2n)^2+(3m+2n)(3m-2n)-9(m+n)^2
= (3m-2n)(3m-2n+3m+2n)-9(m+n)^2
= 6m(3m-2n)-9(m+n)^2
= 6*(-1/2)*{3*(-1/2)-2*1/2}-9*0
= -3*(-5/2)-0
= 15/2

1年前

2

gqergrqe 幼苗

共回答了12个问题 举报

∵m+1/2的绝对值非负数,n^2-n+1/4=(n-1/2)^2也非负数
又:m+1/2的绝对值与n^2-n+1/4互为相反数
∴m+1/2的绝对值=0,n^2-n+1/4=(n-1/2)^2=0
∴m=-1/2,n=1/2
∴m+n=0
(3m-2n)^2+(3m+2n)(3m-2n)-9(m+n)^2
= (3m-2n)(3m-2n+3m+2n...

1年前

2

bike23 花朵

共回答了1976个问题 举报

m+1/2的绝对值与n^2-n+1/4互为相反数,则|m+1/2|+n²-n+1/4=0,则|m+1/2|+(n-1/2)²=0
则m+1/2=0,n-1/2=0,则m=-1/2,n=1/2
(3m-2n)^2+(3m+2n)(3m-2n)-9(m+n)^2
=(3m-2n)(3m-2n+3m+2n)-9(m+n)²
=(3m-2n)...

1年前

0
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