Question 150221
(7x+4)(7x^2+5x+4)
Remember to use the distributive property.
To make it simpler, use a substitution.
Let A=7x+4.
{{{(7x+4)(7x^2+5x+4)=A(7x^2+5x+4)}}}
{{{(7x+4)(7x^2+5x+4)=A7x^2+A5x+A4}}}
That's pretty straight forward. 
Now substitute the original value.
{{{(7x+4)(7x^2+5x+4)=A7x^2+A5x+A4}}}
{{{(7x+4)(7x^2+5x+4)=(7x+4)7x^2+(7x+4)5x+(7x+4)4}}}
Take each term and use the distributive property,
{{{(7x+4)7x^2=(7x)(7x^2)+(4)*(7x^2)=49x^3+28x^2}}}
{{{(7x+4)5x=(7x)(5x)+(4)(5x)=35x^2+20x}}}
{{{(7x+4)4=28x+16}}}
Now put all the parts together,
{{{(7x+4)(7x^2+5x+4)=(7x+4)7x^2+(7x+4)5x+4(7x+4)}}}
{{{(7x+4)(7x^2+5x+4)= (49x^3+28x^2)+ (35x^2+20x)+(28x+16)}}}
Combine all like terms
{{{(7x+4)(7x^2+5x+4)= 49x^3+(28+35)x^2+ (20+28)x+16)}}}
{{{(7x+4)(7x^2+5x+4)= highlight(49x^3+63x^2+48x+16))}}}