Example

Solving {5x2y=10,;y=52x}\left\{5x - 2y = -10,; y = \frac{5}{2}x\right\} by Substitution

Solve the system {5x2y=10y=52x\left\{\begin{array}{l} 5x - 2y = -10 y = \frac{5}{2}x \end{array}\right. using the substitution method. The second equation is already solved for yy, so Step 1 is already complete. Step 2 — Substitute into the other equation. Replace yy in the first equation with 52x\frac{5}{2}x: 5x2(52x)=105x - 2\left(\frac{5}{2}x\right) = -10 Step 3 — Solve the resulting one-variable equation. Simplify the substituted term to get 5x-5x: 5x5x=105x - 5x = -10, which simplifies to 0=100 = -10. Because 0=100 = -10 is a false statement — and the variable has been completely eliminated — the equations are inconsistent. The two lines are parallel and never intersect, so the system has no solution. This example illustrates the algebraic indicator of an inconsistent system: when the substitution process eliminates all variables and produces a false numerical statement such as 0=100 = -10, no ordered pair can satisfy both equations simultaneously. This contrasts with a dependent system, where the substitution process produces a true numerical statement like 0=00 = 0.

0

1

Updated 2026-06-26

Tags

OpenStax

Elementary Algebra @ OpenStax

Ch.5 Systems of Linear Equations - Elementary Algebra @ OpenStax

Algebra

Math

Prealgebra

Related
Learn After