Can someone help with number 4? like how am i supposed to solve this lol what do i do bc i alr know k = -3

Ineed to know the answer to this algebra question.

Aquadratic equation in standard from is written ax^2= bx+c, where a, b and c are real numbers and a is not zero?

In the diagram, the ratios of two pairs of corresponding sides are equal to prove that almn - axyz by the sas similarity theorem, it also needs to be shown that x 6 z un z zz un = 2x zləzz lezy