题目如果 f(x)= ) (x)^2+2,xgt 2 x+a,xleqslant 2 .-|||-x=2 ,当x→2时极限存在,求a的值.-|||-bigcirc A.0-|||-bigcirc B.1-|||-bigcirc C.2-|||-bigcirc D.3-|||-bigcirc E.4题目解答答案