163k views
10 votes
How do you work out this equation

solve simultaneous equations by substitution
9x - 2y = -1
2y = 3x - 5

User Kirlev
by
8.0k points

1 Answer

8 votes

Answer:

x is equal to negative one, and y is equal to negative four.

Explanation:

You can do this by solving one of the equations by either x or y, then substituting it into the other. Let's solve the second one for y:


2y = 3x - 5\\y = (3x - 5)/(2)

Now we'll substitute that into the first equation:


9x - 2y = -1\\9x - 2((3x - 5)/(2)) = -1\\9x - 3x + 5 = -1\\6x + 5 = -1\\6x = -6\\x = -1

So we now know that x is equal to -1. We can simply substitute that into one of the original equations to find y:


2y = 3x - 5\\2y = 3(-1) - 5\\2y = -3 - 5\\2y = -8\\y = -4

We now know that x is equal to -1, and y is equal to -4. We can also check our answer by plugging that -4 into the other equation, and see if we still get -1:


9x - 2y = -1\\9x - 2(-4) = -1\\9x + 8 = -1\\9x = -1 - 8\\9x = -9\\x = -1

So we know that our answer is correct.

User Ahamed Ishak
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.