1.

Find the sum ofdifference of the identity function and the modulus function.

Answer» Let `f:RtoR:f(x)=x` be the identity function.
And, let `g:RtoR:g(x)=|x|` be the modulus function.
Then, dom (f) = R and dom (g)=R.
`:."dom "(f)nn"dom "(g)=RnnR=R`.
(i) dom `(f+g)="dom "(f)nn"dom "(g)=R`.
Now, `(f+g):RtoR` is given by
`(f+g)(x)=f(x)+g(x)`
`=x+|x|=x+{(x",when "xge0),(-x",when "xlt0):}`
`={{:(x+x",when "xge0),(x-x",when "lt0):}={{:(2x",when "xge0),(0",when "xlt0):}`
Hence, `(f+g)(x)={{:(2x",when "xge0),(0",when "xlt0):}`
(ii) dom `(f-g)="dom "(f)nn"dom "(g)=R`.
`:.(f-g)(x)=f(x)=g(x)`
`=x-|x|=x-{{:(x",when "xge0),(-x",when "xlt0):}`
`={{:(x-x",when "xge0),(x+x",when "xlt0):}={{:(0",when "xge0),(2x",when "xlt0):}`
`:.(f-g)(x)={{:(0",when "xge0),(2x",when "xlt0):}`


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