A function evaluation question gives you a rule and asks for its output at a particular input. Replace the input variable with the number in parentheses, then follow every operation in the rule. In Desmos, define the function and enter the requested value. Don’t stop at the number inside a square root; taking the root is part of the rule.
Hints
- Hint 1
In function notation, the number in is the input, not a number to add to the rule. Replace with inside the given expression. What does become?
- Hint 2
A square root is the nonnegative number that squares to the value under the radical sign. Once you’ve calculated the number under the root, take its square root to find the output.
Step-by-step
Substitute, then evaluate in Desmos
Step 1Put the input into the rule
Type into Desmos. To evaluate , replace with , since the number in parentheses is the input: . The multiplies ; it isn’t added again after the .
- Step 2
Read the output
On a new line, type . Desmos shows . The square root covers the entire sum: , and because . Don’t stop at or take the roots of and separately. So the value of is . Choice B.