For a 2×22 \times 22×2 system Ax=bAx=bAx=b, what is the formula for x1x_1x1 by Cramer's Rule?
det(A1)/det(A)\det(A_1) / \det(A)det(A1)/det(A)
det(A)/det(A1)\det(A) / \det(A_1)det(A)/det(A1)
det(A1)×det(A)\det(A_1) \times \det(A)det(A1)×det(A)
A−1bA^{-1}bA−1b