Multiply:-

(x+1) (x^2+x+1)

We must ensure that each term in the second bracket is multiplied by each term in the first bracket.

This can be done as follows.

(x2+x-1) (x+1)

=x2 (x+1) + x (x+1) - 1 (x+1)

distribute each set of brackets.

=x3+x2+x2+x-x-1

and now collect like terms

⇒x3+x2+x2+x

-x

-1=x3+2x2-1

=x3+2x2-1 in standard form

Standard form means writing the expression beginning with the term which has the highest power of the variable. In this case x3 then the next term with the next highest power. In this case + 2x2 and so on until the last term.