Question

The pair of linear equations 2x + 7y = k,kx + 21y = 18 has infinitely many solution if :

(a) = 3 (B) = 6

(c) = 9 (d) = 18​

Answer 1

Answer:

The answer is (B)K=6

Step-by-step explanation:

In the equations

A1=2 B1=7 C1=-K

A2=K B2=21 C2=-18

THESE ARE THE COEFFICIENTS A,B&C ACCORDING TO THE BASIC FORMULA

AX+BY+C=0

If the equations have infinitely many solutions then,

A1/A2=B1/B2=C1/C2

Therefore keeping the values in the formula

2/k=7/21=-k/-18

Now taking 2/k=7/21 separately

2/k=1/3

By cross multiplication,

K=6

Similarly taking 7/21=-k/-18 separately

1/3=k/18

k=18/3 Therefore k=6.

So answer is 6