1. ## Rearanging

Hi I'm a tad vexed by this problem

y(y+z) = a(a-z)

I'm trying to rearange it in terms of z.

I thought I should first multiply out the brackets

y^2 + yz = a^2 -az (where ^2 is squared)

Then take the y^2 away

yz = a^2-y^2-az

Divide by y

z= (a^2 - y^2 - az)y

now how do I get rid of z frm the right side or am I aproaching this wrong, another way I tried was taking the whole right side from the left to make a kind of quadratic equation.

2. We take it from here:

y^2 + yz = a^2 -az

Move all the z on one side and the rest on the other.

yz + az = a^2 - y^2

Factor z;

z(y + a) = a^2 - y^2

Divide by (y+a);

$z = \dfrac{a^2 - y^2}{y + a} = \dfrac{(a - y)(a + y)}{a + y} = a - y$