How to Solve Equations with java?

Question

I have three equations like the following ones:

• x + y + z = 100;
• x + y - z = 50;
• x - y - z = 10;

How can I find the values of

Answer 1

try this, please:

import org.apache.commons.math3.linear.*;
import org.junit.Assert;
import org.junit.Test;

/**
 * Author: Andrea Ciccotta
 */
public class LinearSystemTest extends Assert {

    /**
     * Ax = B
     * 2x + 3y - 2z = 1
     * -x + 7y + 6x = -2
     * 4x - 3y - 5z = 1
     * 

     * it will use the LUDecomposition:
     * LU decomposition:
     * 1. find A = LU where LUx = B
     * 2. solve Ly = B
     * 4. solve Ux = y
     */
    @Test
    public void linearSystem3x3Test() {
        final RealMatrix coefficients = new Array2DRowRealMatrix(new double[][]{{2, 3, -2}, {-1, 7, 6}, {4, -3, -5}});
        final DecompositionSolver solver = new LUDecomposition(coefficients).getSolver();

        final RealVector constants = new ArrayRealVector(new double[]{1, -2, 1}, false);
        final RealVector solution = solver.solve(constants);
        final double[] arraySolution = solution.toArray();

        assertEquals(arraySolution[0], -0.36986301369863006, 0);
        assertEquals(arraySolution[1], 0.1780821917808219, 0);
        assertEquals(arraySolution[2], -0.6027397260273972, 0);
    }

}