Question

Can someone check my answers? I'm not sure I have them all right. Will fan and give a medal for help! attached below

Answer 1

What is the y-intercept of the plane whose equation is 4x + 5y z = 20?

(0, 4, 0) < my answer

(0, 5, 0)

(5, 0, 0)

(0, 0, 4)



Question 2. Which equation has intercepts at X(1, 0, 0), Y(0, 1, 0), and Z(0, 0, 2)?

x y + 2z = 4

3x 2y + 6z = 12

2x 2y + z = 2

4x 4y + z = 4



Question 3. Which equation is equivalent to x + 3y z = 3?

3x + 6y 3z = 6

4x + 12y 4z = 12

2x + 4y 2z = 8

2x + 3y 4z = 12



Question 4.4. Which of the following points lies in the plane 3x 2y + 4z = 12?

(2, 2, 3)

(5, 15, 2)

(4, 16, 2) < my answer

(4, 3,2)

Answer 2

@perl

Answer 3

4x + 5y z = 20 seems to have a typo?

Answer 4

@jim_thompson5910 the first one?

Answer 5

yeah, there are others where it seems like there's a missing symbol

Answer 6

What is the y-intercept of the plane whose equation is 4x + 5y - z = 20?

Answer 7

So you plug x = 0 and z = 0


4x + 5y - z = 20
4*0 + 5y - 0 = 20
5y = 20
y = 4

so yeah it is (0,4,0)

Answer 8

I see it now, it's just a - symbol

Which equation has intercepts at X(1, 0, 0), Y(0, -1, 0), and Z(0, 0, 2)?

Answer 9

that #2^^^

Answer 10

Can you help me out with the others because I don't know them

Answer 11

can you post the updated choices for #2. They are missing symbols

Answer 12

x - y + 2z = 4

3x - 2y + 6z = 12

2x - 2y + z = 2

4x - 4y + z = 4

Answer 13

here is one way to do it: we're given a list of choices, so why not use them to check each point

For instance, choice A is x - y + 2z = 4

if choice A was the answer, then (1,0,0) must be on this plane. Let's check that claim


x - y + 2z = 4
1 - 0 + 2*0 = 4 ... plug in (x,y,z) = (1,0,0)
1 - 0 + 0 = 4
1 = 4 ... this false, so (1,0,0) is NOT on the plane. This cannot be the answer so choice A is out.

Answer 14

do you see how I was able to eliminate choice A?

Answer 15

oh yea I do

Answer 16

I think it might be C

Answer 17

you have to make sure ALL 3 points make the equation true

Answer 18

Let's check that

Answer 19

Checking (1,0,0)

2x - 2y + z = 2
2*1 - 2*0 + 0 = 2
2 = 2 ... works

-------------------------------------------------------

Checking (0, -1, 0)

2x - 2y + z = 2
2*0 - 2*(-1) + 0 = 2
2 = 2 ... works

-------------------------------------------------------

Checking (0, 0, 2)

2x - 2y + z = 2
2*0 - 2*0 + 2 = 2
2 = 2 ... works

Answer 20

since all 3 points make the equation 2x - 2y + z = 2 true, we've confirmed the answer

Answer 21

So I was right it is C? :)

Answer 22

@jim_thompson5910

Answer 23

yes and I show how it's true

Answer 24

Can you help me with 3? @jim_thompson5910
Which equation is equivalent to x + 3y - z = 3?

3x + 6y - 3z = 6

4x + 12y - 4z = 12

2x + 4y - 2z = 8

2x + 3y - 4z = 12

Answer 25

We see '3' on the right side of the original equation.

Look at choice A. Notice how there is a 6 on the right side. What happened going from 3 to 6?

Answer 26

hint: multiplication

Answer 27

Hmmm @jim_thompson5910 is it B?

Answer 28

do you see what I'm asking?

Answer 29

not sure