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# Why is it with function transformations that sometimes horizontal translations are the opposite of what I think they'd be?

Example: In –x^2– 4x+ 5 I would say ok so it has a reflection of the y axis, It moves right 4 units and moves up 5. But the answer is that instead of moving 4 units right, its 4 units LEFT. Why???

### 3 Answers by Expert Tutors

Jason S. | My goal is the success of my students. Knowledge-Patience-HonestyMy goal is the success of my students. K...
4.9 4.9 (115 lesson ratings) (115)
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Take y = x2 and y= (x-4).

The parabolic form is y = a(x MINUS h) PLUS k, where (h, k) is the vertex of the parabola opening up or down depending on the sign of a.

So the vertex is at (0,0) for y = x2 since y = 1(x-0)2 + 0.

Now, for y = (x-4)2, note that the vertex (which is essentially the "handle" for the parabola) is now at
(+4, 0).

So despite the (x MINUS 4) being squared, the x coordinate of the vertex was shifted from 0 to 4, which is a shift to the right of 4.

Now consider y=(x+4)2.

That's really y = (x - (-4))2 + 0.   So the vertex was moved 4 units to the left from (0, 0) to (-4, 0).

Hope this helps.
Andre W. | Friendly tutor for ALL math and physics coursesFriendly tutor for ALL math and physics ...
5.0 5.0 (3 lesson ratings) (3)
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For quadratic functions such as this one, you should complete the square to see how the parabola is shifted and reflected. In your case,

f(x) = –x²– 4x+ 5 = -(x+2)² + 9

The +9 tells us the parabola is shifted up (positive y-direction) by 9 units relative to the origin, the +2 tells us it is shifted left by 2 units (negative x-direction), so the vertex is at (-2,9). The negative sign tells us it opens down (in the negative y-direction).

More generally, if you change a function from f(x) to f(x+A) for any positive constant A, its graph is shifted A units to the left. f(x-A) shifts the graph A units to the right. If you change f(x) to f(x)+A, it shifts it A units up, and f(x)-A is shifted A units down.
Alex V. | College doesn't make you smart. College teaches you to be resourceful.College doesn't make you smart. College ...
4.8 4.8 (73 lesson ratings) (73)
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Y=x^2 is centered around origin.

Assuming your coordinates are traditional (+ to the right and - to the left of the origin)

Analyze y=x^2 - 4x:

To bring y back to the origin, we have to add (move 4x units to the right).

This means y moved -4x units which is 4x to the left.