Math Problem Statement

Solve by élimination méthode to get y1 and y2 equation

Solve by elimination method to get y₁ and y₂ from the given system of equations.

Solution

To solve the system of equations by the elimination method, follow these steps:

The equations provided are:

  1. (120s)y1+518y2=1115\left(-\frac{1}{20} - s \right)y_1 + \frac{5}{18}y_2 = -\frac{1 - 11}{5}
  2. 518y1+(5185)y2=7\frac{5}{18}y_1 + \left(-\frac{5}{18} - 5 \right)y_2 = -7

Step 1: Rewrite the system for simplicity

Let us simplify the constants where possible.

For the first equation: Right-hand side: 1115=105=2\text{Right-hand side: } -\frac{1-11}{5} = -\frac{-10}{5} = 2 So, equation (1) becomes: (120s)y1+518y2=2\left(-\frac{1}{20} - s \right)y_1 + \frac{5}{18}y_2 = 2

The second equation remains: 518y1+(5185)y2=7\frac{5}{18}y_1 + \left(-\frac{5}{18} - 5 \right)y_2 = -7

Step 2: Align the coefficients for elimination

To eliminate one variable, align the coefficients of y1y_1 or y2y_2. Let's eliminate y2y_2.

The coefficients of y2y_2 in the two equations are 518\frac{5}{18} and 5185-\frac{5}{18} - 5. To eliminate y2y_2, we will multiply both equations to match these coefficients.

Multiply the first equation by (5185)-\left(-\frac{5}{18} - 5\right):

(120s)y1(5185)+518y2(5185)=2(5185)\left(-\frac{1}{20} - s \right)y_1 \cdot \left(-\frac{5}{18} - 5\right) + \frac{5}{18}y_2 \cdot \left(-\frac{5}{18} - 5\right) = 2 \cdot \left(-\frac{5}{18} - 5\right)

Multiply the second equation by 518\frac{5}{18}:

518518y1+(5185)518y2=7518\frac{5}{18} \cdot \frac{5}{18}y_1 + \left(-\frac{5}{18} - 5\right) \cdot \frac{5}{18}y_2 = -7 \cdot \frac{5}{18}

Step 3: Solve for y1y_1

After eliminating y2y_2, solve for y1y_1. Substitute y1y_1 into one of the original equations to find y2y_2.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Systems of Equations
Elimination Method

Formulas

Elimination method to solve two-variable equations

Theorems

Basic properties of equality

Suitable Grade Level

Grades 10-12