Need help with functions!!

[galfameg#]

Hi, Currently working on revision for an upcoming algebra class and I just want to make sure I did these problems correctly. Let me know where I went wrong if I did!


The problem asks If f(x) = 4x^2 − x + 4, find the following.

f(a + 1) = 4a^2+7a+7



2f(a) =2(2a^2-a+4)


f(2a) = 4(a^2-a+1)



[f(a)]2 = 4(a^2)^2 - (a^2) + 4


f(a+h) = 4(a+h)^2 - (a+h) +4


]Let me know what you think!

 

[Steven G]

1st one is correct.
2nd is wrong.
3rd is wrong
4th is wrong.
5th is correct.

 

[Harry_the_cat]

The problem asks If f(x) = 4x^2 − x + 4, find the following.

f(a + 1) = 4a^2+7a+7

2f(a) =2(2a^2-a+4) ... should be 4a^2 rather than 2a^2 in the brackets and then I would expand it out

f(2a) = 4(a^2-a+1) ... start again with this one put (2a) wherever you see an x in the original function

[f(a)]2 = 4(a^2)^2 - (a^2) + 4 .... is this meant to be [f(a)]^2 ? ... you have found f(a^2) ... find f(a) first, then square the whole thing ... try again

f(a+h) = 4(a+h)^2 - (a+h) +4

see comments in red