LinearSolve::nosol
LeastSquares::nosol
An error occurs because these equations do not have a solution:
LinearSolve[{{1, 3}, {2, 6}}, {1, 1}]This shows equivalent equations using Solve:
Solve[{x + 3y == 1, 2x + 6y == 1}, {x, y}]This shows a specification of equations that have a solution:
LinearSolve[{{1, 3}, {1, 6}}, {1, 1}]