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[Skyrunner]

Checking the book, 17 is correct.

[da_nang]

But... You're reflecting a line over a point. This means that any line that crosses through that point can serve as a reflection axis when reflecting the line y=-x-3.
For instance, y=5 and x=2. These special cases are simply done by translating the function so the axis matches a coordinate axis, reflect it and then translate back. For x=2, the reflected line is x-7, with y-intercept y=-7
For y=5, the reflected line is y = x+13, y-intercept 13.

For y = x + 3, the reflected line is essentially the same, y=-x-3, y-intercept -3. So you see, for different lines, you get different y-intercepts.

[Darvi]

But... You're reflecting a line over a point. This means that any line that crosses through that point can serve as a reflection axis when reflecting the line y=-x-3.

I have to stop you there. Reflecting a line over a point is as if you reflected it over a parallel line that happens to pass through said point. At a different angle it doesn't reflect anymore.

The reflection is therefore always parallel to the original line. in this case, it's x+y-17=0

[da_nang]

I see. Over here, you typically point out what the reflection axis is. For me, it was not a clear-cut assumption that the axis would be going through the point and be parallel.
So, language barrier, then?

[Darvi]

There is no actual reflection axis. It just happens that central symmetry works like a parallel axis when it comes to lines.

[Skyrunner]

Actually, you can reflect over a point.

This is the official solution.

Spoiler (click to show/hide)

Assume that the reflection of the point (x, y), which is on the original line, is (x₁, y₁). The midpoint of the two points is then (2, 5).

Therefore,

[Darvi]

What she said.

[Descan]

...

What just happened?

[Darvi]

Math happened.

[Skyrunner]

Glory.


Of math.

[RedKing]

...

What just happened?

I'm with you. There were some numbers and some letters and something about the Axis. I think they're planning to invade Poland.

[miauw62]

Had to go to the dentist today. No matter how cliched it is.

BIGASS NEEDLES AND TORTURE TOOLS D:

I managed to survive it tough.

[brainfreez]

Had to go to the dentist today. No matter how cliched it is.

BIGASS NEEDLES AND TORTURE TOOLS D:

I managed to survive it tough.

you managed to survive ? no shit , man .

[kaijyuu]

I think he's just sugarcoating the story so it won't scare us. He actually died.

[Loud Whispers]

I think he's just sugarcoating the story so it won't scare us. He actually died.

No, the dentists didn't let him die.