On Equal Ratio Theorem

Question

If

,

find a.

Find the mistake

By the Equal Ratio Theorem,

\

What is the mistake?

Finding the missing child

In the above calculation, we assume that x + 2y + 4z ¹ 0,

If x + 2y + 4z = 0, we have 2y + 4z = - x,

therefore,

The solution is: a = 1/2 or –1.

Lesson

In using the Equal Ratio Theorem, don’t forget to check whether the denominator is zero or not.