Question

Equation of line passing through the point (1, 2) and perpendicular to the line y = 3x - 1 is

• A. x + 3y + 7 = 0
• B. x + 3y - 7 = 0
• C. x + 3y = 0
• D. x - 3y = 0

Answer 1

Answer: (B)

x + 3y - 7 = 0

$y=3x-1$
General equation of line is $y=mx+c$
$\therefore m=3$
If two lines are perpendicular, then$m_1\cdot m_2=-1$
Slope of line perpendicular to $y=3x-1$ will be $\frac{-1}{3}$
$\therefore$ Equation of line $y=\frac{-1}{3}x+c$
$3y+x=c$
This line passes through the point (1,2)
$\therefore 3\left(2\right)+1=c$
$c=7$
Equation of line becomes
$x+3y=7$
$x+3y-7=0$