Sum of n terms 1x2+2x3+3x4+4x5+...

1/3(n+1)³

Step-by-step explanation:

1x2+2x3+3x4+4x5+...= 1²+1+2²+2+3²+3+...+n²+n+1=

=(1²+2²+3²+...+n²)+(1+2+3+...+n+1)=

=1/6n(n+1)(2n+1)+1/2(n+1)(1+n+1)=

=1/6(n+1)(n(2n+1)+3(n+2))=

=1/6(n+1)(2n²+4n+2)=

=1/6(n+1)*2(n+1)²=

=1/3(n+1)³

answer4 to the second power is 16

and 4 to the third power is 64,

b. 18

step-by-step explanation:

so the equation for this is:

ab^2=ac⋅ad

ab being the top length of 6 and ac being the length of 2 and ad being the length of x. let's plug into the equation:

6^2 = 2x

now lets just solve for x:

36 = 2x

18 = x

i hope that !