An equation of the type ax = b, where a and b are real constants and x is an unknown, is called a linear equation in x. If x1, x2 …, xn are unknowns (called variables) then a relation of the type
where a1, …, an and b are given real constants is called a linear equation in x1,… , xn. The constants a1, …, an are called the coefficients of the variables x1, …, xn respectively. By a solution of equation (10.1) is meant a set of values of x1, …, xn which satisfy it.