lsolve
x=lsolve(L, b)
Finds one solution of the linear system L * x = b where L is an [n x n] lower triangular matrix and b is a [n] column vector.
Try it yourself:
| $1 | a = [-2, 3; 2, 1]
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| $2 | b = [11, 9]
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| $3 | x = lsolve(a, b)
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