A function evaluation question gives you a rule and asks for the output at a specific input, such as . Replace every occurrence of the variable with that input, including any in a denominator. In Desmos, define the rule and evaluate it on the next line. Keep track of which terms are outside the fraction.
Hints
- Hint 1
uses function notation: the number in parentheses is the input. Put in place of in the rule. Where does that put the in this fraction?
- Hint 2
A fraction bar groups the numerator and denominator. Work out the denominator before dividing, and keep the outside the fraction. What would you type on a second Desmos line after defining ?
Step-by-step
Substitute and evaluate in Desmos
Step 1Put the input into the rule
In function notation, means use wherever the rule has . Replace even when it's in the denominator. So:
The stays outside the fraction.
- Step 2
Read the output
Type in Desmos, then type on the next line. Desmos shows . It divides by before adding , so the value of is . Choice C.