If the lines ax + 2y + 1 = 0,bx + 3y + 1 = 0, | vedclass

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(A) Three lines $a_1x + b_1y + c_1 = 0$,$a_2x + b_2y + c_2 = 0$,and $a_3x + b_3y + c_3 = 0$ are concurrent if the determinant of their coefficients is

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Arithmetic Progression

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(A) Three lines $a_1x + b_1y + c_1 = 0$,$a_2x + b_2y + c_2 = 0$,and $a_3x + b_3y + c_3 = 0$ are concurrent if the determinant of their coefficients is zero: $\begin{vmatrix} a & 2 & 1 \ b & 3 & 1 \ c & 4 & 1 \end{vmatrix} = 0$ Expanding along the first row: $a(3 - 4) - 2(b - c) + 1(4b - 3c) = 0$ $-a - 2b + 2c + 4b - 3c = 0$ $-a + 2b - c = 0$ $2b = a + c$ This condition implies that $a, b, c$ are in Arithmetic Progression.

If the lines $ax + 2y + 1 = 0$,$bx + 3y + 1 = 0$,and $cx + 4y + 1 = 0$ are concurrent,then $a, b, c$ are in:

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