When using a perpendicular director, why must the compass opening be greater than 1/2 the length of the segment

Nine more than four times a number is the same as one less than twice the number. find the number?

Write two point-slope equations for the line passing through the points (6, 5) and (3, 1)

Anew test for ra is being developed. the test is administered to 750 patients with ra and 750 without ra. for the sake of the question, assume the prevalence of ra in this population is 50%. of the 750 patients with ra, 575 have a positive result. of the 750 patients without ra, 150 have a positive result. what is the positive predictive value of the new test? a575/(575+150) b. 600/(600+ 150) c. 575/(575+125) d. 600/(600+ 125)