When n is positive number explain why n(n-1) will always be positive

how do i put this into math terms

Alake near the arctic circle is covered by a sheet of ice during the cold winter months. when spring arrives, the ice starts to melt. s(t) models the ice sheet's thickness (in meters) as a function of time tt (in weeks). s(t)=-0.25t+4

Which statements about these triangles is true

Find the solution set of this inequality. enter your answer in interval notation using grouping symbols. |8x-4| ≤ 12