Question

Find the value of 64 x^3+ 125z^3 if 4x+5z =19and x=5

Answer 1

Step-by-step explanation:

4x+5z=19 and x=5

if x=5,now we calculate the value of z,

4x+5z=19 ⇒ 5z=19-(4×5) ⇒z= -1÷5

Now we have to find,

64 x^3+ 125z^3 = (4 x)^3+ (5z)^3 =(5+(-1/5))(25-(5×(-1/5))+1/25

                         = (24/5)(26+(1/25)   (Since, x^3+y^3=(x+y)(x^2-xy+y^2))

                         =(24/5)(651/25)

                         =(15624/125)

 64 x^3+ 125z^3=124.996