题目21.计算y=x^2-1与x+y=1围成的面积A. 5B. (9)/(2)C. -(9)/(2)D. 421.计算$y=x^{2}-1$与x+y=1围成的面积A. 5B. $\frac{9}{2}$C. $-\frac{9}{2}$D. 4题目解答答案B. $\frac{9}{2}$