As for the fifth question in the picture, maybe you (-—Wing—-) were fooled by its appearance. First of all, we need to make a transformation, that is, the numerator and denominator are multiplied at the same time (√( 1+x)+√( 1-x)).

Result: The numerator is 2x, where x will be subtracted from the denominator.

The final result is equal to 2/(√( 1+x)+√( 1-x)), and then set the ε-δ language.

The content behind is the content of the exam. If you don't know it, you will be deducted. .........