If a = (4, -5) and b = (7, -9), what is the length of ab ? a. 6 units b. 5 units c. 8 units d. 7 units

5 (Answer B)

Step-by-step explanation:

As we move from A to B, x increases by 3 and y decreases by 4.  Apply the Pythagorean Theorem:

(length of AB) = √(3² + [-4]²) = 5 (Answer B)

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

the first one, all those points on the line just make a strait line.