Algebra · real student question

Solve 20x - 2 - (4x + 2) = 6 + 2x for x.

Question

Solve for xx:

20x2(4x+2)=6+2x20x-2-(4x+2)=6+2x

Step-by-step solution

  1. Remove the bracket, negating both terms inside. A minus sign in front of a bracket flips the sign of everything within:

    (4x+2)=4x220x24x2=6+2x-(4x+2)=-4x-2\quad\Rightarrow\quad 20x-2-4x-2=6+2x

    Writing 4x+2-4x+2 instead is the standard slip and shifts the answer.

  2. Combine like terms on the left.

    20x4x=16x,22=416x4=6+2x20x-4x=16x,\qquad -2-2=-4\quad\Rightarrow\quad 16x-4=6+2x

  3. Gather the variable terms. Subtract 2x2x from both sides:

    14x4=614x-4=6

  4. Gather the constants. Add 44:

    14x=1014x=10

  5. Divide and reduce.

    x=1014=570.7143x=\frac{10}{14}=\frac57\approx 0.7143

    Always reduce: 1010 and 1414 share the factor 22.

  6. Check exactly. With x=57x=\frac57: the left side is 10072(207+2)=8074=527\frac{100}{7}-2-\left(\frac{20}{7}+2\right)=\frac{80}{7}-4=\frac{52}{7}, and the right side is 6+107=5276+\frac{10}{7}=\frac{52}{7} ✓.

Answer

x=570.7143x=\frac{5}{7}\approx 0.7143

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