Algebra · real student question

Solve the equation (x/5 + 1) times (x/2) = 2488.

Question

Solve for xx:

(x5+1)x2=2488\left(\frac{x}{5}+1\right)\cdot\frac{x}{2}=2488

Step-by-step solution

  1. Multiply out the product. Distributing the x2\frac{x}{2} over the bracket,

    (x5+1)x2=x210+x2\left(\frac{x}{5}+1\right)\frac{x}{2}=\frac{x^2}{10}+\frac{x}{2}

    so the equation is quadratic, not linear — there will be two roots.

  2. Clear the denominators. The least common denominator of 1010 and 22 is 1010, so multiply everything by 1010:

    x2+5x=24880x^2+5x=24880

  3. Put it in standard form.

    x2+5x24880=0x^2+5x-24880=0

  4. Compute the discriminant and check whether the root simplifies.

    Δ=524(1)(24880)=25+99520=99545\Delta=5^2-4(1)(-24880)=25+99520=99545

    Factoring, 99545=54346399545=5\cdot 43\cdot 463 — three distinct primes, no square factor — so 99545\sqrt{99545} cannot be simplified. Numerically 99545=315.50753\sqrt{99545}=315.50753.

  5. Apply the quadratic formula.

    x=5±995452x1=155.2538,x2=160.2538x=\frac{-5\pm\sqrt{99545}}{2}\quad\Rightarrow\quad x_1=155.2538,\quad x_2=-160.2538

    Rounding to 155.20155.20 is not accurate enough: substituting it gives (155.205+1)155.202=2486.30\left(\frac{155.20}{5}+1\right)\frac{155.20}{2}=2486.30, missing the target by about 1.71.7.

  6. Verify with Vieta and by substitution. The roots sum to 5-5 and multiply to 24880-24880, matching b/a-b/a and c/ac/a ✓. And directly, (155.25385+1)155.25382=2488.00\left(\frac{155.2538}{5}+1\right)\frac{155.2538}{2}=2488.00 ✓. If the context requires a positive quantity, take x155.25x\approx 155.25.

Answer

x=5±995452,x155.2538 or x160.2538x=\frac{-5\pm\sqrt{99545}}{2},\qquad x\approx 155.2538\ \text{or}\ x\approx -160.2538

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