Math problem: coordinate

[Electrons]

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Which line is parallel to the y-axis?

1) x=4y
2) x=(2/y)b
3) x=y+6
4) xy=2
5) xy=2+4y^-1

answer is (2). I thought it should be (3). Are they wrong?

 

[Streetwolf]

Which line is parallel to the y-axis?

1) x=4y
2) x=(2/y)b
3) x=y+6
4) xy=2
5) xy=2+4y^-1

answer is (2). I thought it should be (3). Are they wrong?

(1) and (3) right off the bat are strictly linear and have slopes of 4 and 1 respectively. So they are not.

(4) is a hyperbola so that isn't either.

(5) is rewritten as xy + 4/y = 2 ; xy^2 + 4 = 2y ; xy^2 - 2y + 4 = 0. This looks more like a function of y than of x but if you graph it you'll probably see that it doesn't work.

I have no idea what that b is doing in (2).

 

[KTDMD]

Which line is parallel to the y-axis?

1) x=4y
2) x=(2/y)b
3) x=y+6
4) xy=2
5) xy=2+4y^-1

answer is (2). I thought it should be (3). Are they wrong?

None of the above is right. To make a line verticle, you'll need x = a constant value.

 

[Electrons]

I have no idea what that b is doing in (2).

There's a degree symbol superscript on the y, does it make any difference?

 

[Streetwolf]

There's a degree symbol superscript on the y, does it make any difference?

So what is the exact equation then?

What is the 'b' ?

Lines exactly parallel to the y-axis are only of the form: x = a constant.

 

[bigstix808]

Which line is parallel to the y-axis?

1) x=4y
2) x=(2/y)b
3) x=y+6
4) xy=2
5) xy=2+4y^-1

answer is (2). I thought it should be (3). Are they wrong?

agreeing that the only way to get a line || to the Y-axis is with a constant x-value, i would have to say that (5) would be the answer.

(5) xy=(2+4)y^-1 ----> xy=(2+4)/y ----> x=2+4 ----> x=6 🙂

 

[Streetwolf]

agreeing that the only way to get a line || to the Y-axis is with a constant x-value, i would have to say that (5) would be the answer.

(5) xy=(2+4)y^-1 ----> xy=(2+4)/y ----> x=2+4 ----> x=6 🙂

Yeah two mistakes.

1. It isn't (2+4)y^-1, it's 2 + (4y^-1).
2. In your second step (arrow 2) you dropped out the y, when in reality you would end up with either a y^2 on the left or a y^-2 on the right. Of course this step shouldn't even exist due to #1 but it's worth pointing out.

 

[Electrons]

Streetwolf,

That's all there is to the problem for choice 2) I have no idea what that b means, but maybe they mistype it for something.

x=(2/y)b where there is a degree superscript on the y.

Bigstix808,
I couldn't retype it here clearly, but the y^-1 was meant to be "y to the negative 1". I guess I should have re-type it as like the one below.

5) xy=2+4(y^-1)

I see where you guys saying in order for it to parallel, it has to be in the form of x= some number.

Anyway, I think this problem has some typo error and screwing us up. Thanks for helping.

 

[bigstix808]

Yeah two mistakes.

1. It isn't (2+4)y^-1, it's 2 + (4y^-1).
2. In your second step (arrow 2) you dropped out the y, when in reality you would end up with either a y^2 on the left or a y^-2 on the right. Of course this step shouldn't even exist due to #1 but it's worth pointing out.

my B. it's hard doing problems on a computer screen w/o actually writing them down. sad to say i was a math major at one point. calc I, II, and III (check), linear algebra (check), differential equations (check), HS algebra (not so much)😀

 

[Streetwolf]

my B. it's hard doing problems on a computer screen w/o actually writing them down. sad to say i was a math major at one point. calc I, II, and III (check), linear algebra (check), differential equations (check), HS algebra (not so much)😀

I hear you. I always grab a pen/pencil and paper when I have to solve these things. Just so much easier.

If the y has a degree superscript, that could represent a constant. Or, perhaps it represents the y-intercept. And since b also represents the y-intercept, the two would cancel out, leaving x = 2. Just a thought.

In any case I would have chosen (2) given those choices, since the others are CLEARLY not right and (2) at least has a chance of being right since I'm not quite sure what they're doing with it.