a(b-√5)？

=2(√5-2-√5)?

=2×4

=8

Question 27: The cube root of ∵ x-3 =1128y = 2 2/3 = 4.

∴x^3= 128 y^3=4

x^3+y^3+xy

= 128+4+( 128^( 1/3))*(4^( 1/3))

= 132+8

= 140

Note: (128 (1/3)) * (4 (1/3)) means that the cube root of128 is multiplied by the cube root of 4, so this method is used because the cube root cannot be punched.