Question

Val
....
* Choose the correct answer from the given four
options in the following questions 1-3:
1. If the system of equations 2x + 3y = 7;
(a + b) x + (2a - b) y = 21 has infinitely many
solutions, then the values of a and b are:
(A) a = 1, b = 5
(B) a = 5, 6 = 1
(C) a = -1, b = 5
(D) a = 5, b = -1. (1)​

Answer 1

Answer:

(b) a=5 and b=1

Step-by-step explanation:

2x + 3y =7

( a+b) x + ( 2a-b) y = 21

for infinite no. of Sol.

2/a+ b = 3/2a- b = -7/ -21

2/ a+ b= 1/3 , 3/ 2 a- b= 1/3

after solving both we get two eq.

by 1st we get a+ b = 6

by 2 nd we get. 2a - b = 9

by elimination method

add both eq.

a+ b = 6

2a- b = 9

3 a = 15

a= 5

putting this value of x in eq. 1st

b= 1