作业帮1+3=(1+3)*2/2;1+3+5=(1+5)*3;1+3+5+7=(1+7)*4/2````,则1+3+5+7+9+```+(2n-1)等于?a n*nb (n+1)*(n+1)c (1+n)*n/2d (n+1)*n/2
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1+3=(1+3)*2/2;1+3+5=(1+5)*3;1+3+5+7=(1+7)*4/2````,则1+3+5+7+9+```+(2n-1)等于?a n*nb (n+1)*(n+1)c (1+n)*n/2d (n+1)*n/2
1+3=(1+3)*2/2;1+3+5=(1+5)*3;1+3+5+7=(1+7)*4/2````,则1+3+5+7+9+```+(2n-1)等于?
a n*n
b (n+1)*(n+1)
c (1+n)*n/2
d (n+1)*n/2
1+3=(1+3)*2/2;1+3+5=(1+5)*3;1+3+5+7=(1+7)*4/2````,则1+3+5+7+9+```+(2n-1)等于?a n*nb (n+1)*(n+1)c (1+n)*n/2d (n+1)*n/2
前三个可以看出规律
和=（首项+末项）*项数/2
项数=（末项+1）/2
所以 1+3+5+7+9+```+(2n-1)
=（1+2n-1)*(2n/2)/2
=2n*n/2
=n*n
选a
a
1+3+5+7+9+```+(2n-1)
=（1+2n-1)*(2n/2)/2
=2n*n/2
=n*n
a n*n
1+2+3-4-5+1+1+2+3=
1+3-5*4^2-3=
1 2 3 4 5=1
1()2()3()4()5=1
1+1-2+3-4+5=?
2+3= 5-3= 2-1=
1=5 2=1 5 3=2 1 5 4=3 2 1 5 5=?
计算(+5/2)-(-5/3)=-5/1(-5/2)-(-5/3)=5/12/1-3/1=6/1(-2/1)-3/1=-6/1
-5X-2/1=3/1(X-3/1)
3+1/2+1/3+1/4+5=?
求和Sn=1*(1/3)+3*(1/3)^2+5*(1/3)^3+.+(2n-1)*(1/3)^n求和Sn=1*(1/3) + 3*(1/3)^2 + 5*(1/3)^3 +.+(2n-1)*(1/3)^n
1+2=3 4+5=?
(1).3x+5/2=2x-1/3
1+3/2=5/2对吗
1+2=3?
D=3 1 -1 2-5 1 3 -42 0 1 -11 -5 3 -3
2/3+3/4x=1 5/8x+2/3×1/2=1
1+1=?还有1+2+3+4+5=?