Question

The value of k for which the lines 5x + 7y=3 and 15x + 21y = k coincide is ______.

Options

• 9

• 5

• 7

• 18

Answer 1

The value of k for which the lines 5x + 7y=3 and 15x + 21y = k coincide is 9.

Explanation:-

For lines to coincide:

`a_1/a_2=b_1/b_2=c_1/c_2`

so, `5/15=7/21=(-3)/(-k)`

`1/3 = 1/3 = (3)/(k)`

i.e. k = 9