简算: ① ②102.31×59
(1)解方程: ( x + 1 ) 2 - 4 = 0 ;
(2)解不等式组: - 2 x + 3 ⩽ 1 x - 1 < x 3 + 1 .
解方程组: 3 x - y = - 4 x - 2 y = - 3 .
解方程组和不等式组:
(1) x + y = 0 2 x - y = 3 ;
(2) 3 x + 6 > 0 x - 2 < - x .
计算: ( x + 2 y ) 2 + ( x - 2 y ) ( x + 2 y ) + x ( x - 4 y ) .
化简: ( a a - 1 + 5 a + 9 a 2 - 1 ) ÷ a + 3 a - 1 .