Algebra · real student question

Solve the absolute value equation |4x + 3| = 2.

Question

Solve

4x+3=2|4x+3|=2

Step-by-step solution

  1. Confirm two solutions are expected. The right-hand side 22 is positive, so the expression inside the bars can be either +2+2 or 2-2. A positive right-hand side always yields two solutions; only a right-hand side of 00 gives one, and a negative one gives none.

  2. Write the two cases. From A=2|A|=2 we get A=2A=2 or A=2A=-2, with A=4x+3A=4x+3:

    4x+3=2or4x+3=24x+3=2\qquad\text{or}\qquad 4x+3=-2

  3. Solve the first case. Subtract 33, then divide by 44:

    4x=1x=144x=-1\quad\Longrightarrow\quad x=-\frac{1}{4}

  4. Solve the second case. Subtract 33 from 2-2 this time:

    4x=5x=544x=-5\quad\Longrightarrow\quad x=-\frac{5}{4}

  5. Verify both roots. Substituting each value back reproduces 22:

    4(14)+3=1+3=2\left|4\left(-\tfrac14\right)+3\right|=|-1+3|=2\qquad\checkmark
    4(54)+3=5+3=2=2\left|4\left(-\tfrac54\right)+3\right|=|-5+3|=|-2|=2\qquad\checkmark

    Notice the two roots sit symmetrically about x=34x=-\tfrac34, the value that makes the inside zero — that symmetry is a useful sanity check for every equation of this shape.

Answer

x=14orx=54x=-\frac{1}{4}\quad\text{or}\quad x=-\frac{5}{4}

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