Respuesta :

v= x*(10-2x)(8-2x)

for greatest volume,  differentiate v w.r.t x and equate to 0,

dv/dx= (10-2x)(8-2x) + x(-2)(8-2x)+ x(10-2x)(-2)=0

you get x from solving the quadratic equation. volume will be max at that x