把下列各式分解因式:
(1)7x2-63
(2)x2-14x+49.
(1)7x2-63,
=7(x2-9),
=7(x+3)(x-3);
(2)x2-14x+49=(x-7)2.
北半球台风可航半园内的特点和避航法是:()
A.右半园、风向右转、左尾受风驶离
B.右半园、风向右转、右首受风驶离
C.左半园、风向左转、右尾受风驶离
D.左半园、风向左转、左首受风驶离