Solve the following system of equations using the elimination method.
2x + 4y = 10

–2x + y = –15
Question 10 options:

A)

(–2,7)

B)

(7,–1)

C)

(3,1)

D)

(8,–3)

you can't solve x because it is 2 linear equation and you only have one equation

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