You are Here: Home

Help need in P2 plz watch

1. i don't know how to do any of these questions

The functions f and g are defined by

f:x -> |x - a|
g:x -> |4x + a|

where 'a' is a positive constant

a) on the same diagram scketch the graphs of f ang g, showing lcearily the coordinates of any points at which your graphs meet the axes

(how can u plot it if u dont even know the value of 'a')

b) use algebra to find, in terms of a, the coordinates of the point at which the graphs of f and g intersect

c) find an expression for fg(x)

d) solve, for x in terms of a, the equation
fg(x)=3a

Thank you
2. can u follow what i've done?
Attached Images

3. (Original post by k0rrupter)
i don't know how to do any of these questions

The functions f and g are defined by

f:x -> |x - a|
g:x -> |4x + a|

where 'a' is a positive constant

a) on the same diagram scketch the graphs of f ang g, showing lcearily the coordinates of any points at which your graphs meet the axes

(how can u plot it if u dont even know the value of 'a')

b) use algebra to find, in terms of a, the coordinates of the point at which the graphs of f and g intersect

c) find an expression for fg(x)

d) solve, for x in terms of a, the equation
fg(x)=3a

Thank you
If they intersect, then |4x+a| = |x-a|. This implies either 4x + a = x - a, i.e x = -2a/3, or 4x+a = a-x, i.e x = 0.

f(x) = |x-a| so f(g(x)) = |g(x)-a| = ||4x+a|-a|.

If f(g(x)) = 3a then 3a = ||4x+a|-a|. So 3a = |4x+a| - a so 4a = |4x+a| so x = 3a/4 or -5a/4. You can reject -3a because a is >0.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 27, 2004
Today on TSR

Life lessons uni will teach you

Questionable decision-making and constant surprises

University open days

1. Loughborough University
Fri, 21 Sep '18
2. University of Cambridge
Fri, 21 Sep '18
3. Richmond, The American International University in London
Fri, 21 Sep '18
Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE