I have problems in solving multivariable calculus

Following are my question:

I don't know how to solve equations from 2 to 5

I need step by steps solution

1. [20 marks] Calculate the following limits: z 1+02 01 +22 || 2 | 3 (b) lim 1+03 || 20 || 1 (a) lim 2. [20 marks] Find the quadratic approximation of f(x) and an upper bound (as tight as possible) on its maximum error over D for f(x) 1+2102 2 +11 & D= {1 ER2 : ||2||20