中等math-u02-d04
A student expands (x - 3)^2 and writes x^2 - 9. The term that is missing is:
A. -6x✓ 答案
B. +6x
C. -3x
D. +3x
解說
(x - 3)^2 = x^2 - 6x + 9. Only the middle term was dropped, and its sign is negative because it is 2 x (-3).
(x - 3)^2 = x^2 - 6x + 9. Only the middle term was dropped, and its sign is negative because it is 2 x (-3).