Question

the equation of the straight line passing through the point (2,-4) and perpendicular to the line 8x-4y+7=0 is a) x+2y+6=0 b) x-2y+6=0 c) 2x+y+6=0 d) 2x-y+6=0 please answer my question fast

Answer 1

first of all ,by hit and trial put (2,-4)
on putting in a option
2+2(-4)+6=0
2-8+6=0
point satisfies the equation of line ,hence answer is option (a)
now checks whether both lines are perpendicular or not
let m1 is slope of given line
m1 = -(coefficient of x / coefficient of y)
m1= -(8/-4)
m1 = 2

m2 is slope of option a
m2 = -1/2
if bothes linr are perpendicular then m1×m2=-1
lets check 2×(-1/2) = -1
hence both lines are perpendicular

answer is option (a)

Answer 2

you have to find slope of the given equation first by -a/b where a=2 and b= -4 . then by slope point form,ie y-y1 = m(x - x1) where y1= -4 and x1 = 2. hence ans is (c)2x + y + 6