Q. 4 B4.2( 24 Votes )
Find equation of line joining (3, 1) and (9, 3) using determinants.
Answer :
Equation of line joining points (x1, y1) & (x2, y2) is given by 
= 0
Given points are (3, 1) and (9, 3)
Equation of line is given by 
= 0
⇒ 1/2 × [3 × (3 × 1 – y × 1) – 1 × (9 × 1 – x × 1) + 1 × (9 × y – x × 3)] = 0
⇒ [3 × (3 – y) – 1 × (9 – x) + (9y – 3x)] = 0 × 2
⇒ (9 – 3y – 9 + x + 9y – 3x) = 0
⇒ 6y – 2x = 0
⇒ 2x – 6y = 0 ⇒ x – 3y = 0
∴ Required Equation of line is x – 3y = 0
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