Algebra · real student question

The function f(x) = |x - 1| + 5 is translated 4 units up and 2 units right. Write the equation of the new function.

Question

The function f(x)=x1+5f(x)=|x-1|+5 is translated 44 units up and 22 units right. Write the equation of the translated function.

Step-by-step solution

  1. Read the vertex from the given form. In f(x)=xh+kf(x)=|x-h|+k the vertex is (h,k)(h,k), so f(x)=x1+5f(x)=|x-1|+5 has its corner at

    (1,5)(1,5)

    Both translations will move this single point, and the arms of the V keep slopes ±1\pm 1 throughout.

  2. Shift right 2 by substituting xx2x\to x-2.

    (x2)1+5=x3+5\left|(x-2)-1\right|+5=|x-3|+5

    Notice the inside constant changed from 11 to 33: shifting right increases the value of hh, even though the operation performed was a subtraction inside the bars.

  3. Shift up 4 by adding 4 outside.

    x3+5+4=x3+9|x-3|+5+4=|x-3|+9

  4. Write the answer and confirm the vertex moved correctly.

    f(x)=x3+9,vertex (3,9)f(x)=|x-3|+9,\qquad \text{vertex }(3,9)

    From (1,5)(1,5) to (3,9)(3,9) is right 22 and up 44 \checkmark — the vertex displacement is the cleanest verification available.

  5. Sanity-check a non-vertex point. The original passes through (0,6)(0,6) since 01+5=6|0-1|+5=6. Translating that point right 22 and up 44 predicts (2,10)(2,10), and the new formula gives 23+9=1+9=10  |2-3|+9=1+9=10\;\checkmark. Note also that the whole graph now sits at or above y=9y=9, so this function has no xx-intercepts at all.

Answer

f(x)=x3+9f(x)=|x-3|+9

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