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Which of the following pair of linear equations has / have many infinite solutions?

A. 9x+3y+12=09x + 3y + 12 = 0; and 18x+6y+24=018x + 6y + 24 = 0

B. 2x−3y=132x - 3y = 13; and 7x−2y=207x - 2y = 20

C. x+y=5x + y = 5; and 2x+2y=102x + 2y = 10

D. 3x+y−3=03x + y - 3 = 0; and 2x+23y=22x + \dfrac{2}{3}y = 2

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

Infinite solutions require a1a2=b1b2=c1c2\dfrac{a_1}{a_2} = \dfrac{b_1}{b_2} = \dfrac{c_1}{c_2}.

A: all ratios equal 1/21/2, so infinite.

B: 2/7≠−3/−22/7 \neq -3/-2, so a unique solution.

C: all ratios equal 1/21/2, so infinite.

D: multiplying the first by 2/32/3 gives the second exactly, so infinite.

Hence A, C and D only.

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