The question you are referring to is MJ07 P5 Q2b. It is done as follows:
- assume a value of 6+- 0.4.
- square of 6 is 36.
- 6+0.4= 6.4. square of 6.4= 40.96
- to find the error in the square, 40.96-36= 4.96
- hence the final answer to be recorded in the table is 36+- 5.0
Note that i put 5.0 instead of 4.96. The mark scheme allows a range of 4.6-5.0. You should use the same number of decimal places that the question uses.