1. 36(a+b)^2 - 49(a-b(^2
2.x^2 - y^2 - 9z + 6yz
3. find the value if x=16 & y=5
x^2 + y^2 + xy
line means division)
x^3 - y^3

-13a^2 + 170ab - 13b^2.

Step-by-step explanation:

1.  36(a+b)^2 - 49(a-b)^2

This is the difference of 2 squares: a^2 - b^2 = (a + b)(a - b).

36(a+b)^2 - 49(a-b)^2

= (6(a + b) + 7(a - b))(  6(a + b) - 7(a - b))

= (6a  + 7a + 6b - 7b)( 6a - 7a + 6b + 7b)

= (13a - b)(-a + 13b)

If you require the expansion of this it is:

-13a^2 + 170ab - 13b^2.