Question 49121
functions are VERY VERY simple things to use. They just look frightening because they are a more "professional" way of writing maths and to be honest a fair few maths teachers are rubbish at teaching too. Anyway...


All that f(x) =5x-1 means is that given the value "x", as quoted in f(x), then we have to multiply it by 5 and then subtract 1 from that.


eg f(2) means multiply it by 5 and then subtract 1.
--> f(x) =5x-1
--> f(2) = 5(2)-1
--> f(2) = 10-1
--> f(2) = 9


eg f(-6) means multiply it by 5 and then subtract 1.
--> f(x) =5x-1
--> f(-6) = 5(-6)-1
--> f(-6) = -30-1
--> f(-6) = -31


and so f(x) =5x-1  find f(a)
--> f(x) =5x-1
--> f(a) =5a-1 
DONE


and finally
--> f(x) =5x-1
--> f(a-2) =5(a-2)-1
--> f(a-2) =5a-10-1
--> f(a-2) =5a-11
DONE


When asked to do questions like this, the above is ALL you do. I hope you see how easy it is now. Hope this helps.


jon.