Back to: Algebra 1
How to evaluate expressions?
To evaluate an algebraic expression, you need to substitute a number for each variable and perform the arithmetic operations. In the example below, the variable x is equal to 3, therefore 32 + 2(3) + 5 = 9 + 6 + 5 = 20. If we know the value of our variables, we can replace the variables with their values and then evaluate the expression.
Example: Evaluate the expression, x2 + 2x + 5 when x = 3.
Answer: 32 + 2(3) + 5 = 9 + 6 + 5 = 20.
Example: Evaluate the expression, 3x2 + 4x + 1 when x = 2.
Answer: 3(2)2 + 4(2) + 1 = 12 + 8 + 1= 21
Example: Evaluate the expression, 4x + 3y when x = 3 and y = 4.
Answer: 4(3) + 3(4) = 12 + 12 = 24
Example: Evaluate the expression, 2x2 + 3y2 + 4x – 2y when x = 3 and y = 5.
Answer: 2(3)2 + 3(5)2 + 4(3) – 2(5) = 18 + 75 + 12 – 10 = 95