Algebra · real student question

Solve the equation 5(-5 + n) - (-5n + 1) = -2 and give the answer as a fraction.

Question

Solve

5(5+n)(5n+1)=25(-5 + n) - (-5n + 1) = -2

Giving the answer as an exact fraction.

Step-by-step solution

  1. Expand the first bracket.

    5(5+n)=25+5n5(-5 + n) = -25 + 5n

  2. Distribute the minus over the second bracket. The leading sign flips both terms inside:

    (5n+1)=+5n1-(-5n + 1) = +5n - 1

    Getting 5n1-5n - 1 here instead would make the nn terms cancel and produce a false "no solution", which is the classic failure mode for this problem.

  3. Combine like terms.

    25+5n+5n1=210n26=2-25 + 5n + 5n - 1 = -2 \quad\Longrightarrow\quad 10n - 26 = -2

  4. Isolate n.

    10n=24n=2410=125=2.410n = 24 \quad\Longrightarrow\quad n = \frac{24}{10} = \frac{12}{5} = 2.4

    Reducing 2410\tfrac{24}{10} by the common factor 22 gives the fraction in lowest terms.

  5. Check by substitution. 5(5+2.4)=5(2.6)=135\left(-5 + 2.4\right) = 5(-2.6) = -13, and (5(2.4)+1)=(12+1)=11-\left(-5(2.4) + 1\right) = -(-12 + 1) = 11. Their sum is 13+11=2-13 + 11 = -2, matching the right-hand side.

Answer

n=125=2.4n = \frac{12}{5} = 2.4

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