What's the perimeter using Pythagorean theorem

An assembly consists of two mechanical components. suppose that the probabilities that the first and second components meet specifications are 0.87 and 0.84. assume that the components are independent. determine the probability mass function of the number of components in the assembly that meet specifications. x

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?