Without actually calculating the value of cubes find the value of $(1)^3+(2)^3+2(4)^3+(-5)^3+(-6)^3$. Also write the identity used Without actually calculating the value of cubes find the value of $(1)^3+(2)^3+2(4)^3+(-5)^3+(-6)^3$. 
Also write the identity used 

use the sum of cubes of continuous integers: $\dfrac{n^2 (n+1)^2}{ 4}$ , this is the same as $1^3 + 2^3 +\cdots+n^3$. You can use this. But you need to have coefficients of 1 in front of your cubes, so split the $(2)4^3=4^3+4^3$. Leave the negatives at the end and do the same thing
