Question

if
$\frac{x}{3} = \frac{y}{5} = \frac{z}{7}$
then what is the value of
$( {z}^{2} - {x }^{2} + {y}^{2} ) \div {2y}^{2}$

Answer 1

First find the value of x and z in terms of y
x=3y/5
z=7y/5

Now,
(z^2 - x^2 + y^2) / 2y^2
[(49y^2 /25) - (9y^2 /25) + y^2] / 2y^2
[(49y^2 - 9y^2 +25y^2) / 25] / 2y^2
(65y^2 /25)/2y^2
65y^2 / 50y^2
13/10