The formula of a volume of a cuboid:
[tex]V=lwh[/tex]
l - length
w - width
h - height
We have:
l = (x + 4) cm
w = (x + 1) cm
h = 3 cm
Substitute:
[tex]V=(x+4)(x+1)(3)[/tex] use distributive property
[tex]V=(x+4)(3x+3)[/tex]
[tex]V=(x)(3x)+(x)(3)+(4)(3x)+(4)(3)[/tex]
[tex]V=3x^2+3x+12x+12[/tex] combine like terms
[tex]\boxed{V=3x^2+15x+12}[/tex]
