Answer:
21
Explanation:
You want the value of the expression 2f(-3)-f(4), given that f(x) = 3x²-x+ 5.
Function evaluation
A function is evaluated by putting the argument where the variable is, and simplifying the result. Polynomials are often easier to evaluate if they are written in Horner form.
f(x) = 3x² -x +5
f(x) = (3x -1)x +5
The values we need are ...
f(-3) = (3(-3) -1)(-3) +5 = (-10)(-3) +5 = 35
f(4) = (3(4) -1)(4) +5 = (11)(4) +5 = 49
Then the expression of interest has the value ...
2f(-3) -f(4) = 2(35) -49 = 70 -49
2f(-3) -f(4) = 21