A discrete time signal $x[n]$ is defined in terms of unit impulse function as follows:
$$x[n]= 1-\sum_{r=3}^\infty \delta[n-1-r]$$
If $x[n]$ is expressed in terms of the unit step function as $x[n]=u[an-b]$ then find the values of $a$ and $b$. I have tried to solve but not able to solve it further. Please check this image:
Please correct my grammar if there is any mistake.