Whats the distance between (-4 ,3) and (5,4)

Which term best describes the association between variables a and b? no association a negative linear association a positive linear association a nonlinear association a scatterplot with an x axis labeled, variable a from zero to ten in increments of two and the y axis labeled, variable b from zero to one hundred forty in increments of twenty with fifteen points in a positive trend.

Ineed i been stuck on this question since yesterday

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)