What is an extraneous solution?

Of four points are collinear, they are also coplanar

The number of potato chips in a bag is normally distributed with a mean of 71 and a standard deviation of 2. approximately what percent of bags contain between 69 and 73 potato chips? approximately 68% approximately 71% approximately 95% approximately 99.7%

Determine which expressions represent real numbers and which expressions represent complex number. asaaap! plis!