What you’ll learn
Evaluate multi-variable expressions.
Key idea
Multiply each coefficient by its corresponding variable before adding terms.
Each coefficient multiplies its own labeled variable; unequal coefficients and values prevent swapped substitutions from coincidentally passing.
Worked example
Enter the exact value or ordered values in the format requested below.
Evaluate 2x+3y for x=2, y=9. Enter the exact value.
- Substitute x=2 in 2x and y=9 in 3y.
- 2×2+3×9=4+27=31.
Answer: 31
Quick Check
Evaluate a worked attempt at evaluate multi-variable expressions, identify the first invalid step, and provide the correction.
A student writes Step 1: x=6, y=1 in 2x+3y. Step 2: 2(1)+3(6)=20. Locate the first invalid step and correct the value.