Question

The angle between the line 2x+y+1=0 and x+ky+5=0 is 90° then k=

Answer 1

Answer: The value of k would be -2.

Step-by-step explanation:

When two line makes an angle of 90 degree, the product of slope of one line and slope of another line equals to -1.

So,

m1*m2= -1

The slope of the line 2x+y+1=0 is -2 i.e. m1= -2

The slope of the other line x+ky+5=0 is -1/k

Now,

m1*m2= -1

Plugging the value of m1 and m2, we get:

-2*(-1/k)= -1

2/k= -1

k= -2