211k views
5 votes
One number is 4 more than 2 times another. Their product is 30. Find the numbers. The numbers are ? and ? or ?and ? .

User Kamae
by
8.7k points

1 Answer

5 votes

Let the first number be x and y be the second.

Then we habe:

I) x - 4 = 2y

II) x*y = 30

We can rewrite equation I as:

x = 2y + 4

Applying this result on equation II, we have:

(2y + 4)*y = 30

2y² + 4y = 30

2y² + 4y - 30 = 0

y² + 2y - 15 = 0


\begin{gathered} y_+=\frac{2+\sqrt[]{(2)^2-4\cdot1\cdot(-15)}}{2} \\ y_+=\frac{2+\sqrt[]{64}}{2} \\ y_+=(10)/(2) \\ y_+=5 \end{gathered}

The second root is negative and don't satisfy equations I and II, then we can discard it.

Replacing y with 5 in equation I, we have:

x - 4 = 2*5

x = 2*5 + 4

x = 14

User Lordzuko
by
8.3k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories