Consider the functions f(x) = x2 − 13 and g(x) = x + 5. What is the value of (f − g)(−4)?

Question

kainui · Answer

f(x)-g(x) looks like (x2-13)-(x+5). Plug in -4 for x and you will find your answer.

asnaseer · Answer

@Kainui is correct. you are given:$$f(x)=x^2-13$$$$g(x)=x+5$$and are asked to compute "f-g" when x=-4. there are two ways of doing this. you can either first find f(-4) and g(-4) and then substract one from other like so:$$f(-4)=(-4)^2-13=16-13=3$$$$g(-4)=-4+5=1$$$$f(-4)-g(-4)=3-1=2$$or you can create a new function that represents "f-g", call it "h", and work out h(-4) as follows:$$h(x)=f(x)-g(x)=(x^2-13)-(x+5)=x^2-13-x-5=x^2-x-18$$$$h(-4)=(-4)^2-(-4)-18=16+4-18=2$$