Which of the following are possible ways to eliminate a variable by multiplying first?
−x + 4y = 5
9x − 3y = 21
A. Multiply the first equation by 3 and the second equation by 4.
B. Multiply the first equation by 4 and the second equation by 3.
C. Multiply the first equation by 3 and the second equation by 9.
D. Multiply the first equation by 9 and the second equation by 4.
E. Multiply the second equation by 9.
F. Multiply the first equation by 9.