Which of the following is an arithmetic sequence? a. -4, -2, 0, 2, b. -8, -4, -2, -1, c. -4, -3, -1, 2, d. -4, 0, -4, 0,

I believe the answer would be A because an arithmetic sequence consists of  a constant difference between terms.

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4