Week 2 Question/resource help

Course Q&A Math for Machine Learning Linear Algebra for Machine Learning and Data Sc...
1

Hello I am week 2 lesson labeled “solving system of equations with more variables”
Is there a breakdown of the operations performed for each variable solved for? I noticed the operations jump to the answer and leave out details when solving for the answer.
video :46 , you will hear “use the first equation to remove ‘a’ from the others”. Is there a breakdown of the steps in greater detail or additional resources you can recommend to help me? I feel like I look at the answer and it takes a bit to figure out how he got there. This is a simple example but also relevant in the gradient video.
For ex:
a + b + 2c =12
3a -3b -c =3
2a-b + 6c =24

next part of the equation shows:
a +b +2c = 12
-2b -7/3c = -11

  • 3/2b + c =0

My question is do we have office hours where we can ask questions on items we get stuck on or is it forum only?

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Forum only. The instructor is not involved in operating the course.

I’ll take a look at your question and see about posting a detailed workup.

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Thank you.

When solving for the gaussian elimination problem, is there an order to how its solved.
First: 1/2R 1
Second: R2 - 2R1
Etc

4

Here are the steps in the solution in detail, starting from time mark 0:29

Notes:
(R?) refers to an entire row. Operations on that row are applied to each element.
→ means “replaces”.

(R2) / 3 → R2
(R3) / 2 → R3
Gives the result shown at 0:37.

(R2) - (R1) → (R2)
(R3) - (R1) → (R3)
Gives the result shown at 0:48

(R2) / -2 → (R2)
(R3) / -(3/2) → (R3)
Gives the result shown at 1:18

(R3) - (R2) → (R3)
Gives the result shown at 1:28

(R3) * (-6/11), gives c = 3
Substitute c into (R2), gives b = 2.
Substitute b and c into (R1), gives a = 4.

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5

Hello @jhash3

I suggest that you rewatch the video: “Solving Non-Singular Systems of Linear Equations”. Although it focuses on solving systems with two variables, it provides useful intuition for addressing systems with more variables, as the stages to solve the problem are similar.

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6

Thank you, this is helpful.

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