Question:easy

Let \(A = [\begin{array}{cc}-5 & -3 \\ 2 & 1\end{array}]\). The Row transformation \(R_1\rightarrow R_1+3R_2\) will transform matrix A into

Show Hint

Carry out the row operation and read off the shape of the new matrix.
Updated On: Oct 1, 2026
  • an upper triangular matrix
  • a lower triangular matrix
  • an identity matrix
  • a singular matrix
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Do the operation.
New first row: $(-5 + 3 \cdot 2,\ -3 + 3 \cdot 1) = (1, 0)$.

Step 2: Write the matrix.
\[ \begin{pmatrix} 1 & 0 \\ 2 & 1 \end{pmatrix} \]

Step 3: Test each option.
Upper triangular needs the bottom-left entry to be 0, but it is 2, so (A) is out. Identity needs 0 there, so (C) is out. Determinant $= 1 - 0 = 1 \neq 0$, so (D) is out. The top-right entry is 0, so it is lower triangular.

Final Answer:
Option (B). \[ \boxed{\text{Lower triangular matrix}} \]
Was this answer helpful?
0