Evaluate the following algebraic expression using the given values for the variables
1. - 2x + 1, when x = 2
2. x-7xy + 6y. when x = 3 and y = 5
3. 4x+6y, when x=-2 and y = -1
(x + y)
4. If x = 4, find the numerical value of ( x + y )​