Question

if 2x+ay=4 and bx+4y=8 are parallel lines such that a and b are positive integers then number of possible pairs of (a,b) is.

a.3
b.4
c.5
d.7​

Answer 1

Answer:

b. 4

Explanation:

ay=-2x+4

y=(-2/a)x+(4/a)

m1 = - 2/a

bx+4y=8

4y=-bx+8

y=(-b/4)x + 2

m2 = - b/4

As the lines are parallel,

m1=m2

-2/a=-b/4

ab=8

clearly pairs are (1,8) , (8,1) , (2,4) , (4,2)