## shahzadjalbani 3 years ago what is f(x) ? if f(x-1)=x^2+3x+5

1. pratu043

I'm not sure, but I think its (x + 1)^2 + 3(x - 1) + 5

2. princeofwetlot

f(x) = f[(x -1) + 1]

3. princeofwetlot

yup that's right @pratu043 :)

explain @pratu043

5. princeofwetlot

lol look at what i wrote...f(x-1 + 1) = f(x + 0) = f(x) since f(x-1) = x^2 + 3x + 5 f(x - 1 + 1) = (x+1)^2 + 3(x+1) + 5 got the logic?

1 and 1 will be cancelled then there will f(x) I didn't get.

7. princeofwetlot

hmmm you get that f(x-1 + 1) = f(x) right?

8. princeofwetlot

now let a = x-1 f(a) = a^2 + 3a + 5 agree?

yes...

10. princeofwetlot

now like i said f(x) = f(x-1 + 1) = f(a+1) therefore f(a + 1) = (a+ 1)^2 + 3(a+1) + 5

11. princeofwetlot

oops i made a mistake o.O

12. princeofwetlot

substituting a made me confused -_-

which mistake.......

I am also confused ...........

15. princeofwetlot

substituting will actually make it complicated..let me start again do you get that f[(x-1) + 1] = f(x)?

yes now I am clear thank you...........

17. princeofwetlot

really? lol..great