2.  To find the numerical value of the expression, simply substitute the variables in the expression with the given number. Evaluate: 2x + 7, if x = 4 Substitute 4 for x. 2(4) + 7 8 + 7 = 15

3. Evaluate: 3x + 2y – 9, if x = 4, y = 2 Substitute x and y 3(4) + 2(2) – 9 Follow the orders of operation. 12 + 4 – 9 16 – 9 7

4. Evaluate: 2x – 3xy + 4y, if x = 3, y = -5 Substitute in the numbers. 2(3) – 3(3)(-5) + 4(-5) Use correct order of operations. 6 + 45 – 20 51 – 20 31

5. Evaluate: 2x 2 + y 2 – 5, if x=-5, y=7 Substitute for x and y 2(-5) + (7) 2 – 5 -10 + 49 – 5 39 – 5 34!!!!

6. Incorrect Evaluate x 2, if x = -3 -3 2 = -9 Evaluate –x 2, if x = -3 -(-3) 2 = 3 2 =9 Correct Evaluate x 2, if x = -3 (-3) 2 = 9 Evaluate –x 2, if x = -3 -(-3) 2 = -(9) = -9