Answer:
[tex]7x^2+28x[/tex]
Step-by-step explanation:
[tex]7x(x+4)\\\\Multiplication\ is\ distributive\ on\ addition\\\\\Rightarrow 7x(x+4)=7(x\times x+x\times 4)\\\\7x(x+4)=7(x^2+4x)\\\\Multiplication\ is\ distributive\ on\ addition\\\\\Rightarrow 7x(x+4)==7\times x^2+7\times 4x\\\\7x(x+4)=7x^2+28x[/tex]
