Background
Consider a system of linear equations, here three equations of three variables x1, x2, x3. The general form looks something like this, with given numbers a
ij and bi:
a11x1 + a12x2 + a13x3 = b1
a21x1 + a22x2 + a23x3 = b2
a31x1 + a32x2 + a33x3 = b3
Or, using matrices and vectors:
According to Cramer's rule, the solution can be given in terms of determinants, i.e.
xi =det(Ai)/det(A)
where Ai is the matrix obtained from A by replacing the i-th column with the vector b. For 3 * 3 determinants,you can use the following simple formula to calculate the determinant:
Obviously, Cramer's rule only works for det(A) != 0. One can show that the system has a unique solution if and only if det(A) != 0. Otherwise, the system has either no solution or infinitely many solutions.
Please note that one would not use Cramer's rule to solve a large system of linear equations, simply because calculating a single determinant is as time-consuming as solving the complete system by a more efficient algorithm.
Problem
Given a system of three linear equations in three variables, use Cramer's rule to find the unique solution if it exists. More precisely, calculate the determinants of the Ai and of A and decide by looking at det(A) whether the system has a unique solution. If it does, calculate the solution according to Cramer's rule.