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标题: XDJM 求助一道数学题多谢啦 [打印本页]

作者: TopTerminator 时间: 2011-11-19 07:06 标题: XDJM 求助一道数学题多谢啦

此题是prep里的，我的问题是：答案中有两个明确的解，应该选C 还是选E?

44.3852-!-item-!-187;#058&003578

In the xy-plane, at what two points does the graph of y = (x + a)(x + b) intersect the x-axis?

(1) a + b = -1

(2) The graph intersects the y-axis at (0, -6).

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【答案】C

【思路】intersect the x-axis, 其方程式的y=0

y=(x+a)(x+b) y=
+x(a+b)+ab
(1) y=
-x+ab ----------------------------------------------------------------------insufficient
(2) -6=ab-----------------------------------------------------------------------insufficient

(1)(2)

x^2-x-6=0 x=3 or-2 -----------------------------------------------------------------sufficient

作者: CloverJackier 时间: 2011-11-20 06:40

当然是c了阿
问了你是那两个阿

作者: TopTerminator 时间: 2011-11-20 20:26

不好意思我呆逼啦

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