Algebra · real student question

The function f(x) = |x + 2| - 3 is reflected in the x-axis and then translated 2 units down. Write the equation of the new function.

Question

The function f(x)=x+23f(x)=|x+2|-3 is reflected in the xx-axis and then translated 22 units down. Write the equation of the resulting function.

Step-by-step solution

  1. Read the starting vertex. f(x)=x+23f(x)=|x+2|-3 opens upward with vertex (2,3)(-2,-3), and it crosses the xx-axis twice, where x+2=3|x+2|=3, that is at x=5x=-5 and x=1x=1.

  2. Reflect in the xx-axis: negate everything. Every output changes sign, so the whole right-hand side gets a minus sign in front:

    f(x)=(x+23)=x+2+3-f(x)=-\left(|x+2|-3\right)=-|x+2|+3

    The constant flips from 3-3 to +3+3. Distributing that minus over both terms is the entire difficulty of the problem.

  3. Translate 2 units down. Subtract 22 from the reflected function:

    x+2+32=x+2+1-|x+2|+3-2=-|x+2|+1

  4. Final equation and its shape.

    f(x)=x+2+1,vertex (2,1), opens downwardf(x)=-|x+2|+1,\qquad \text{vertex }(-2,1),\ \text{opens downward}

    The vertex went from (2,3)(-2,-3) to (2,3)(-2,3) under reflection, then down 22 to (2,1)(-2,1).

  5. Verify with points and intercepts. Original (0,1)(0,-1) reflects to (0,1)(0,1) then shifts to (0,1)(0,-1); the formula gives 0+2+1=2+1=1  -|0+2|+1=-2+1=-1\;\checkmark. The new xx-intercepts satisfy x+2=1|x+2|=1, so x=3x=-3 and x=1x=-1 — the two roots have moved inward from {5,1}\{-5,1\}, consistent with a downward-opening V whose peak is only 11 unit above the axis.

Answer

f(x)=x+2+1f(x)=-|x+2|+1

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