Added book examples

C14/quadratic_solver_function.c

@@ -0,0 +1,24 @@
+int SolveQuadraticEquation(float a, float b, float c, float *x1, float *x2)
+{
+    float d;    // For storing b^2 - 4*a*c
+
+    if ( a == 0)    // Not a quadratie
+    {
+        return -1;
+    }
+
+    // calculate and store b*b-4*a*c for testing ans use later (if OK)
+    d = b*b - 4*a*c;
+
+    if ( d < 0 )
+    {
+        return -1;  // Complex
+    }
+
+    // If we have got to here, we can calculate x1 and x2
+    *x1 = ( -b + sqrt (d)) / (2 * a);  // Note the use of the * before x1 & x2
+    *x2 = ( -b - sqrt (d)) / (2 * a);  // to write to the relevant memory locations
+
+    // As we got here OK, return 0 to indicate all is OK
+    return 0;
+}