Who was the first cartoon character to be given a star on the Hollywood Walk of Fame?

Who invented the telephone?

If a>b, then a² > b² .

The determinant of a 2×2 matrix can be zero.

The lines 2x - 3y = 5 and 3x + 2y = 7 are perpendicular to each other.

In any set of data, the standard deviation is always less than the variance.