Numerical Analysis/LU decomposition concept quiz

Choose the best answer for each question:

1 The LU decomposition is

The name of an algorithm to solve a linear system.
A matrix decomposition which writes a matrix as the product of a lower triangular matrix and an upper triangular matrix.
The same as a QR decomposition.
None of those

2 Is it true that any matrix can be factorized to LU form without pivoting?

Yes
No

3 If A = LU then, det(a) equals:

-det(L)*det(U)
Cannot say anything
None of those

4 The computational cost of the LU decomposition of an matrix is:

O()
O()
O()
O()

5 The number of operations to solve Ax=b when we know L, U is

O()
O()
O()
O()