中等MATH-ALGE-005
What are the solutions of the simultaneous equations x + y = 7 and xy = 12?
A. (3, 4) only
B. (4, 3) only
C. (6, 1) and (1, 6)
D. (3, 4) and (4, 3)✓ 答案
解說
The numbers add to 7 and multiply to 12, so they are 3 and 4. Both ordered pairs work because the equations treat x and y symmetrically. (6, 1) multiplies to 6, not 12.