MHB Solving 3r(r+1)=r(r+1)(r+2)-r(r-1)(r+1) and Finding r(r+1) Sum

[Harry2]

Hey,
Please may someone help me.
How can I show that 3r(r+1) is equal to r(r+1)(r+2) - r(r-1)(r+1) and then I would find the total sum of r(r+1).
Thanks in advance for any help.

 

[Greg]

Have you tried expanding r(r+1)(r+2) - r(r-1)(r+1)?

To find the sum, notice that each 'r' term on the right is 1 less than an 'r' term on the left.

 

[MarkFL]

To show:

$$3r(r+1)=r(r+1)(r+2) - r(r-1)(r+1)$$

try factoring the RHS. :)

 

[Harry2]

To show:

$$3r(r+1)=r(r+1)(r+2) - r(r-1)(r+1)$$

try factoring the RHS. :)

I just thought you couldn't use the right hand side first because it was a show that question. Thanks both of you!