Question

In order to solve the following system of equations by addition, which of the following could you do before adding the equations so that one variable will be eliminated when you add them ?

3x -6y = -15
-2x + 5y = 14
A. Multiply the top equation by 2 and the bottom one by 3.
B. Multiply the top equation by -3 and the bottom one by 2.
C. Multiply the top equation by 2.
D. Multiply the bottoms equation by 6.

Answer 1

To solve the question, the both equations should have a positive value and a negative value with same number. Then one variable can be eliminated.

To eliminate X term first, we should multiply the first equation by 2 and second one by 3.
Then,
6X - 12Y = -30
-6X + 15Y = 70

Or

To eliminate Y term first, we should multiply the first equation by 5 and second one by 6.
Then,
15X - 30Y = -75
-12X + 30Y = 84

According to the choices given 'A' is the correct answer.