Can anyone help with this I found this quite confusing​

9^2 + 12^2 = 15^2

draw the 9 cm side and the 12 cm side with a right angle between them. the 15 cm side will fit to form a right triangle

Step-by-step explanation:

geometry: triangles

solvers

lessons

answers archive

call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

25.45584

if you was gonna solve for a, a is a   < -12