当多项式m的平方-mn=15-搜答案-智慧作业帮

m^2-mn=21mn-n^2=15两式相加m^2-n^2=36两式相减m^2-2mn+n^2=6

(2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)先去括号=2mn+2m+3n-3mn-2n+2m-m-4n-mn合并同类项=-2mn+3m-3n=-2mn+3(m-n)把m-n=2,

m²-mn=153m²-3mn=451式mn-n²=-62mn-2n²=-122式1式+2式得到:3m²-3mn+2mn-2n²=45-12

解（-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn）=-2mn+2m+3n-3mn-2n+2m-m-4n-mn=-2mn-3mn-mn+2m+2m-m+3n-2n-4n=-6mn+3

用x^2表示x的2次方3x^2+my-8-(-nx^2+2y+7)=3x^2+nx^2+my-2y-8-7=(3+n)x^2+(m-2)y-15其中不含x、y项,则含x、y的项系数等于零,这些项就不存

晕M平方-MN=21,MN-N平方=-15两个式子相加得:M平方-N平方=6两个式子相减得:M平方-2MN+N平方=36

1、m^2-mn=21.(1)mn-n^2=-15.(2)用(1)-(2)得：m^2-2mn+n^2=21-(-15)=36.2、当x=1时,ax^3+bx+7=4,将x=1代入ax^3+bx+7=4

∵m²+m-1=0　　∴m²=1-m　　∴m³+2m²+2012　　=m³+2m²+2012　　=m(1-m)+2m²+2012　

m^2+m-1=0m^2=1-mm的3次方+2m的平方+2000=m^3+2m^2+2000=m(1-m)+2m^2+2000=m^2+m+2000=1-m+m+2000=2001

3m的平方-mn-2n的平方=3m²-3mn+2mn-2n²=3(m²-mn)+2(mn-n²)=3×15+2×(-6)=45-12=33

m的平方-mn=21,mn-n的平方=负15所以:m^2-mn-(mn-n^2)=m^2-2mn+n^2=36

m²-mn=21mn-n²=-15两式相减得：m²-2mn+n²=36两式相加得：m²-n²=6

原式=m²-[(9k+1)/3]mn-3n²-6∵不含mn项∴mn项的系数(9k+1)/3=0故k=-1/9

-5m²n+（2mn²+5m²n）-2（3m²-mn²)=-5m²n+2mn²+5m²n-6m²+2mn

m²-mn=12(1)mn-n²=15(2)(1)+(2)m²-n²=12+15=27(1)-(2)m²-2mn+n²=12-15=-3

m^2n-2mn^2+mn=mn(m-2n+1)

-2mn+2m+3n-3mn-2n+2m-4n-m-mn=-6mn+3m-3n=-6mn+3(m-n)=6+9=15

（m+2）^2+|m-2n|=0(m+2)^2=0m=-2|m-2n|=0m=2n=-2n=-13mn-13n^2-5mn+15m^2-2n^2=6-13-10+60-2=41

(2m^2n-2mn^2)/mn=2mn(m-n)/mn=2(m-n)=4

m+n=3多项式2m的平方+4mn+2n的平方-3m+1=2m^2+4mn+2n^2-3m+1=2(m^2+2mn+n^2)-3m+1=2(m+n)^2-3m+1=2*3^2-3m+1=19-3m