math (need help badly)
posted by rita .
the vertices of triangle DEF are D(5,12)and E(2,7) and F(8,4)
Triangle DEF undergoes an enlargement with the centre ,O, and scale factors k.Its image is D`E`F` where D(5,12)arrow D`(7.5,18)
a)How do i detremine the value of k

It looks to me like the new triangle is 1.5 times larger. All primed coordinates are 1.5 times the original. The center of the expansion is the origin (O).
The answer is k=1.5