Algebra · real student question

Solve the absolute value equation |5 - x| = 5.

Question

Solve

5x=5|5-x|=5

Step-by-step solution

  1. Read the inside expression carefully. The quantity inside the bars is 5x5-x, not x5x-5. Since 5x=x5|5-x|=|x-5| you could flip it, but there is no need — the two-case method works with either form as long as you keep the signs straight.

  2. Write the two cases. Because the right-hand side 55 is positive:

    5x=5or5x=55-x=5\qquad\text{or}\qquad 5-x=-5

  3. Solve the first case. Subtracting 55 from both sides leaves x=0-x=0, hence

    x=0x=0

  4. Solve the second case. Subtract 55 to get x=10-x=-10, then multiply by 1-1:

    x=10x=10

  5. Verify and note the symmetry. 50=5|5-0|=5 \checkmark and 510=5=5|5-10|=|-5|=5 \checkmark. Both answers lie 55 units from x=5x=5, the point where the inside vanishes — every equation xa=c|x-a|=c has solutions a±ca\pm c, which here reads 5±55\pm 5.

Answer

x=0orx=10x=0\quad\text{or}\quad x=10

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