Question

find the value of x3-27y3+27xy+27 ​

Answer 1

hi mate,

solution:

x³-27y³+27xy+27

= (((x3) - 33y3) + 27xy) + 27

Step : Checking for a perfect cube : 2.1

= x³+27xy-27y³+27 is not a perfect cube

Final result :

x3 + 27xy - 27y3 + 27

or..

if question is Find the value of x^3-27y^3-343-27xy when x=3y+7

then

The given equation is:

x^{3}-27y^{3}-343-27xy

Putting x= 3y+7 in the above equation, we have

(3y+7)^{3}-27y^{3}-343-27(3y+7)y

Using (a+b)^{3}=a^{3}+b^{3}+3ab(a+b), we have

=27y^{3}+343+63y(3y+7)-27y^{3}-343-27(3y^{2}+7y)

=189y^{2}+441y-81y^{2}-189y

=108y^{2}+252y

which is the required value.

i hope it helps you.