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Course: MAP Recommended Practice>Unit 19

Lesson 27: Systems of equations with graphing

Systems of equations with graphing: chores

Graphical Systems Application Problem. Created by Sal Khan and Monterey Institute for Technology and Education.

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• why do you need a graph, it whould much easier to do it in your head?
• For this equation, yes it is way easier to do in your head. But much of what you'll do in stats or macroeconomics will be far more complicated. This is a just a simplified version so you learn the concept.
• I can't figure out how to graph these equations, no matter how many videos I watch about this topic. Can anybody explain?
• To graph these system of equations, you have to graph the unknowns using the y intercept, and the coefficient of x to figure out how the graph grows. You graph the other equation overlapping the first equation on the graph, and the point where the two graphs intersect is the solution.
• Anyone else solve this in their head in the first minute? :) I sort of just did it logically, is Sal just trying to show us how to do it a different way?
• Does anyone else agree that they explain all the easy questions in the videos and tell us to do all the hard ones in the test? You keep forwarding the video because it's too easy and when you do the test you end up scratching your head and staring at the questions.
• guys is it just me or is the problem in this video so easy.
• Ok, so I think I'm getting it.

The easiest way is doing it with your head - since this is an easy question.

A more complicated way is to graph it...

But is there a way on solving it/finding a solution with just the equation?
• But sometimes in like Algebra 1, you learn parabolas and they are definitely harder to solve in your head and that is when you do the graphing method. But for problems like this I agree with you; algebraically it is much easier.
• I figured this problem out in like the first minute, why would we need to put it on the graph when I can solve it faster in my head?
• The video is about how to solve a system of equations using graphing. If he didn't do the graphing, it wouldn't accomplish the goal of the video. And, not all problems will be solvable in your head. You need to learn this and the other techniques for solving a system of equations.
• At , why is there -B on the right side?
• The negative sign represents -1. So -B is basically -1 * B.
(1 vote)
• What is x + y =z
• you forgot to put the negative 10 its actually 1170
• doing the substitution method I get a=20 and b=30. Why?
• I think you may have mixed something up in your calculation.
A+B=50
A=B+10 Subsituting B+10 for A in the first equation,
(B+10)+B = 50 No subtract 10 from both sides
B+B=40
2B=40 Divide both sides by 2
B=20
Now put 20 in for B in A+B=50, so
A+20=50
A=30

I hope that helps