 - synthesis_ys[synthesis_n-2]) / (synthesis_xs[synthesis_n-1] - synthesis_xs[synthesis_n-2]);

    synthesis_system = document.getElementById("synthesis_system");
    synthesis_system.innerHTML = "P(x<sub>1</sub>)' = "+A[0][3].toFixed(1)+"a + "+A[0][2].toFixed(1)+"b + "+A[0][1].toFixed(1)+"c = "+B[0].toFixed(1);
    synthesis_system.innerHTML += "<br>";
    synthesis_system.innerHTML += "P(x<sub>1</sub>) = "+A[1][3].toFixed(1)+"a + "+A[1][2].toFixed(1)+"b + "+A[1][1].toFixed(1)+"c + "+A[1][0].toFixed(1)+"d