A box has dimensions x + 5 by x + 3 by x + 7. Determine the volume and the surface area.?

Question

IM SOO LOST GUYS PLEASE HELP

Answer 1

Volume(V) = (x+5)(x+3)(x+7)

V = (x+5)(x^2+ 10x+21)

V = x^3 + 10x^2 + 21x + 5x^2 + 50x + 105

V = x^3 + 15x^2 + 71x + 105

Surface Area (SA)  = 2[((x+5)(x+3)] + 2[(x+5)(x+7)] + 2[(x+3)(x+7)]

SA = 2{x^2 + 8x +15 + x^2+12x + 35 + x^2 + 10x + 21}

SA = 2{3x^2 + 30x + 71}

SA = 6x^2 + 60x + 142

Answer 2

Just use the normal formulas with these unknown lengths:

V = lwh

V = (x + 5)(x + 3)(x + 7)

V = (x² + 8x + 15)(x + 7)

V = x³ + 7x² + 8x² + 56x + 15x + 105

V = x³ + 15x² + 71x + 105

SA = 2(lw + lh + hw)

SA = 2[(x+5)(x+3) + (x+5)(x+7) + (x+3)(x+7)]

SA = 2(x² + 8x + 15 + x² + 12x + 35 + x² + 10x + 21)

SA = 2(3x² + 30x + 71)

SA = 6x² + 60x + 142

Since you don't know what x is in the start, you still don't know what x is at the end.  But now you have the formula for getting V and SA so if you're given an x, you can plug them in and get V and SA.

Answer 3

V=lwh

V=(x+5)(x+3)(x+7)

V=(x^2+8x+15)(x+7)

V=x^3+7x^2+8x^2+56x+15x+105

V=x^3+15x^2+71x+105

SA=2(lw+lh+wh)

SA=2((x+5)(x+3)+(x+5)(x+7)+(x+3)(x+7))

SA=2(x^2+8x+15+x^2+12x+35+x^2+10x+21)

SA=2(3x^2+30x+71)

SA=6x^2+60+142