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# Can you answer this composite functions question? watch

1. Given that for all values of x,

f(x) = 3x+p
g(x) = px+4
and fg(x) = 6x+q

where p and q are constants.

Work out the values of p and q.
2. p = 2 and q = 14

Also where did you get this question from? And what exam board are you doing for Math?
3. (Original post by ky_1652)
p = 2 and q = 14

Also where did you get this question from? And what exam board are you doing for Math?
provide working out you donkey.
4. (Original post by Sanket.z.meerkat)
Given that for all values of x,

f(x) = 3x+p
g(x) = px+4
and fg(x) = 6x+q

where p and q are constants.

Work out the values of p and q.
Hi, so firstly as it is composite you need to put g in F. So 3(px+4) + p

Expand and simplify to get

3px + 12 + p
Then make that equal to fg[x] you were given

3px+12+p = 6x + q

Compare coefficients of x

3p=6 so p=2. Then 12+p = q so q = 14

Hope that is clear
5. (Original post by BTAnonymous)
provide working out you donkey.
6. you can write fg (x) as f [g (x)] so this will mean;
fg (x) = 3 (g (x)) + p
fg (x) = 3 (px + 4) + p
fg (x) = 3px + 12 +p
now the trick given is the coefficient of x in fg (x) they have given...the coefficient is 6 that means that p has to be a number that when multiplied by 3 we get 6 and that means p = 2 and u can get q by 12 + p....
hope you understand this 😊

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