In mathematics, a linear equation is an equation that may be put in the form a₁x₁+…+aₙxₙ+b=0, where x₁,…,xₙ are the variables (or unknowns), and b,a₁,…,aₙ are the coefficients, which are often real numbers. The coefficients may be considered as parameters of the equation and may be arbitrary expressions, provided they do not contain any of the variables. To yield a meaningful equation, the coefficients a₁,…,aₙ are required to not all be zero.