Qualification > Sciences

Maths & Physics Help

<< < (12/74) > >>

IGCSE Master:
Functions:

f:x = 2x - 1   and   g:x = x²-1

Find:

f-¹(x)


gf(x)

astarmathsandphysics:
f=2x-1
Make x the subject
f+1 =2x so (f+1)/2=x
Now swap f and x
(x+1)/2=f
Now replace f by f^-1 to give (x+1)/2=f^-1

g(x)=x^2-1 so g(f)=f^2-1 but f(x)=2x-1
so g(f(x))=(2x-1)^2-1
                =(2x-1)(2x-1)-1
                =4x^2-2x-2x+1-1
                =4x^2-4x
             

qwerty:
thanks! i think i get it. so:

f(x) = 3 x - 1

f^-1(x) would then be:

f = 3x-1
f + 1 = 3x
f+1/3 = x
swap
x+1/3 = f
f^-1 = x+1/3

is that correct??

thanks a lot!!!

astarmathsandphysics:
should be (x+1)/3=f^-1(x)
x+1 has to be divided by 3 not just 1 divided by 3

qwerty:
oh i get it! thanks a lot!

Navigation

[0] Message Index

[#] Next page

[*] Previous page