Mathematics in Senior One: Judgment Proposition

If m 2+n 2+a 2+b 2 = 0, the real number mnab is all zero.

This is a true proposition.

Because of m? ≥0，n？ ≥0，a？ ≥0，b？ ≥0, so: to make the above formula M 2+N 2+A 2+B 2 = 0 hold,

It must be like this: m=n=a=b=0.

The four sides of a square are equal.

This is also a true proposition. This is according to the definition (property) of a square: all four sides of a square are equal, and all four internal angles are right angles.