suppose we want to choose 3 letters without replacement from the 4 letters A, B,C, D how many ways can this be done if the order of choice os relevant

Segment an is an altitude of right δabc with a right angle at a. if ab = 2, squared 5 in and nc = 1 in, find bn, an, ac.

What is the value of the discriminant, b2 ? 4ac, for the quadratic equation 0 = x2 ? 4x + 5, and what does it mean about the number of real solutions the equation has?

How many and of which kind of roots does the equation f(x)=2x^4−9x^3+17x^2−16x+6 have?