A nonlinear equation does not produce a straight line and the exponent is to the second power or more. x square plus 3y =5 is an example of a nonlinear equation.
x[x+1] squared Simplified is, to my knowledge, x squared plus ( x + 1) squared
(a + x^2)(b + y^2)
It is a quadratic expression in the variable x.
X = √63
If x is equal to 5, then x squared plus 25 is equal to 50.
8 + X SQUARED
It is a quadratic expression in the variables x and y.