How do you read, write decimals through thousanths

Can someone me with these two circle theorem questions asap?

For problems 29 - 31 the graph of a quadratic function y=ax^2 + bx + c is shown. tell whether the discriminant of ax^2 + bx + c = 0 is positive, negative, or zero.

The coordinates r(1, -3), s(3, -1) t(5, -7) form what type of polygon? a right triangle an acute triangle an equilateral triangle an obtuse triangle