If a1=7and an=-2an1 then find the value of a5

If the slope of one line equals the slope of another line then ? a) the two lines are intersecting lines b) the two lines are perpendicular lines c) the two lines are parallel lines d) the two lines always have very steep slopes

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Show your workcan a right triangle have this sides? *how to prove it without using the pythagorean theorema*