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题库 / Prep2007E2-DS-129
If t is a positive integer and r is the remainder when ~$t^2 + 5t + 6$~ is divided by 7, what is the value of r ?
(1) When t is divided by 7, the remainder is 6.
(2) When t2 is divided by 7, the remainder is 1.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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（2）假设t=7k+m，发现m=1和6都能使t^2除以7余1，所以并不能确定m等于多少（当时忽视了m=6）
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