What is a 2nd degree equation?
We call the 2nd degree equation in unknown x, every equation of the form:
ax^{2} + bx + c = 0; The, B, ç GO and 
Examples:
x^{2 } 5x + 6 = 0 is a 2nd degree equation with The = 1, B = 5 and ç = 6.
6x^{2}  x  1 = 0 is a 2nd degree equation with The = 6, B = 1 and ç = 1.
7x^{2}  x = 0 is a 2nd degree equation with The = 7, B = 1 and ç = 0.
x^{2}  36 = 0 is a 2nd degree equation with The = 1, B = 0 and ç = 36.
In equations written in the form ax² + bx + ç = 0 (normal form or reduced form of an equation of the 2nd degree in the unknown x) we call The, B and ç in coefficients.
The is always the coefficient of x²;
B is always the coefficient of x,
ç is the coefficient or independent term.
Complete and incomplete equations
An equation of the 2nd degree is complete When B and ç are nonzero. Examples:
x²  9x + 20 = 0 and x² + 10x  16 = 0 are complete equations.
An equation of the 2nd degree is incomplete When B or ç is equal to zero, or when both are equal to zero. Examples:


