Question

Need help with the final step:: Let the function f(x) be defined by the equation y = f(x), where x and f(x) are real numbers.
f(x) = 4 − x^2

f(9) = -77
f(-7) = -45
f(k) = 4-k^2
f(k2 − 8) = ??

Answer 1

Basically you just plug in the entire input expression in place of the x

so f(k2 - 8) = 4 - (k2 - 8)^2

Answer 2

suppose to have read as f(k^2-8)=

Answer 3

Still valid if you read the answer the same way. =)

f(k^2 - 8) = 4 - (k^2 - 8)^2