h = w + 4 ;
V = h × w × l ;
Then, 4200 = ( w + 4 ) × w × 30 ;
4200 ÷ 30 = ( w + 4 ) × w ;
140 = ( w + 4 ) × w ;
w^2 + 4w - 140 = 0 ;
For ax^2 + bx + c = 0, the value of x is given by: ;
In our case, a = 1 ; b = 4 ; c = - 140
Roots are - 14 and 10 ;
The correct answer is w = 10inches because w > 0 ;
Finally, h = 14 inches .
