We have the following expression given:
[tex](4y^3+28y^2)+(y+7)[/tex]We can start selecting as common factor 4y^2 and we got:
[tex]4y^2(y+7)+(y+7)[/tex]Now we can select y+7 as common factor and we got:
[tex](y+7)\left\lbrack 4y^2+1\right\rbrack [/tex]So then our final answer would be:
[tex](y+7)(4y^2+1)[/tex]