Question

A line through A(-2,6) and B(4,b) is perpendicular to the line 2x - 4y = 5. The value of b is ___.

• A. -6
• B. 6
• C. 8
• D. -8

Answer 1

The correct option is A -6

Slope of the line AB = $\frac{b-6}{4+2}$

= $\frac{b-6}{6}$

Slope of line $2x-4y=5$ is

$-4y=-2x+5$

$y=\frac{1}{2}x-\frac{5}{4}$ [ slope is $\frac{1}{2}$]

Since the lines are perpendicular

$\frac{b-6}{6}\times \frac{1}{2}$ = -1

$\Rightarrow b-6=-12orb=-6$