Question

If system of equation 2x + 3y = 7 and 20x + (a+b) y = 28 has infinitely many solution, then

A. a = 2b

B. b = 2a

C. a + 2b = 0

D. 2a + b = 0

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Answer 1

Answer:

b=2a option(B)

Step-by-step explanation:

Please make minor correction in the question:

If system of equation 2a + 3y = 7 and 20x + (a+b) y = 28 has infinitely many solution, then

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2x+3y-7=0

2ax+(a+b)y-28=0

For  infinitely many solutions:

a1/a2=b1/b2=c1/c2

Here a1=2,b1=3,c1=-7

and a2=2a,b2=a+b, c2=-28

So 2/2a=3/(a+b)=-7/28

1/a = 3/(a+b)  = - 1/4

a+b=3a

b=2a option (B)