Question

Which expression helps you find the length x of a side of a rectangle that has a diagonal of 15 units and a width of 9 units?

A x^2 = 15^2 – 9^2
B x^2 = (15 + 9)^2
C x^2 = 15^2 + 9^2
D x^2 = (15 – 9)^2

Answer 1

A. x^2 = 15^2 - 9^2

Here's why:
c^2 = a^2 + b^2

from the question:
15^2 = 9^2 + x^2

15^2 - 9^2 = x^2 which is similar to answer in A.