Standard form for quadratic equations is:
0 = ax² + bx + c
To make Alessandro's first equation in standard form, you must make the constant on the left side of the equation 0.
To do this, we should add 6 to each side to cancel out the -6 on the left side of the equation, making its value 0.
Alessandro's new equation is:
-6 + 6 = x² + 4x - 1 + 6
If we simplify this equation, we get:
0 = x² + 4x + 5
Therefore, knowing that the equation above is in the form ax² + bx + c, we can determine that the value of c in Alessandro's new equation is 5.