Algebra · real student question

Solve (x + 1) x 1.76566975 = 25.

Question

Solve (x+1)1.76566975=25(x+1)\cdot 1.76566975 = 25 for xx.

Step-by-step solution

  1. Treat (x + 1) as a single unknown. The whole bracket is multiplied by one constant, so there is no need to distribute. Let u=x+1u = x+1; then 1.76566975u=251.76566975\,u = 25.

  2. Divide by the multiplier. u=x+1=251.76566975.u = x+1 = \frac{25}{1.76566975}. Undoing a multiplication with a division is the only inverse step needed at this stage.

  3. Evaluate the quotient exactly. Writing 1.76566975=706267940000001.76566975 = \tfrac{7062679}{4000000} turns the division into 2540000007062679=1000000007062679=14.15893318\frac{25 \cdot 4000000}{7062679} = \frac{100000000}{7062679} = 14.15893318\ldots Note the eighth digit: a decimal division truncated too early gives 14.158936414.1589364, which is wrong from the seventh significant figure onward.

  4. Subtract 1 to recover x. x=10000000070626791=92937321706267913.15893318.x = \frac{100000000}{7062679} - 1 = \frac{92937321}{7062679} \approx 13.15893318.

  5. Verify by multiplying back. (13.15893318+1)1.76566975=14.158933181.76566975=25.0000000(13.15893318+1) \cdot 1.76566975 = 14.15893318 \cdot 1.76566975 = 25.0000000, so the answer closes to eight decimals.

  6. Note where the multiplier came from. 1.76566975=0.791.151.31.31.151.76566975 = 0.79 \cdot 1.15 \cdot 1.3 \cdot 1.3 \cdot 1.15 exactly, so this equation is the 'solve' companion to collapsing that chain of five percentage factors.

Answer

x=10000000070626791=92937321706267913.15893318x = \frac{100000000}{7062679} - 1 = \frac{92937321}{7062679} \approx 13.15893318

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