设平面区域D由 x=0 ,y=0 +y=dfrac (1)(2) ,x+y=1 围成,记 _(1)=iint (ln )^3(x+y)dxdy --|||-_(2)=iint ((x+y))^3dxdy _(3)=iint (sin )^3(x+y)dxdy ,则I1,I2,I3之间的关系为 () .-|||-(A) _(1)lt (I)_(2)lt (I)_(3) (B) _(3)lt (I)_(2)lt (I)_(1)-|||-(C) _(1)lt (I)_(3)lt (I)_(2) (D) _(3)lt (I)_(1)lt (I)_(2)

2、设A和B是任意两个概率不为零的互斥事件,则下列结论中肯定正确的是 __-|||-(A)A与B互斥 (B)A与B不互斥-|||-(C) P(AB)=P(A)P(B) (D) P(A-B)=P(A)

(2)(2007204)二元函数f(x,y)在点(0,0)处可微的一个充分条件是-|||-__-|||-A. lim _((x,y)arrow (0,0))[ f(x,y)-f(0,0)] =0-|||-B. lim _(xarrow 0)dfrac (f(x,0)-f(0,0))(x)=0, 且 lim _(xarrow 0)dfrac (f(0,y)-f(0,0))(y)=0-|||-C. lim _((x,y)arrow (0,0))dfrac (f(x,y)-f(0,0))(sqrt {{x)^2+(y)^2}}=0-|||-D. lim _(xarrow 0)[ (f)_(x)(x,0)-(f)_(x)(0,0)] =0, 且 lim _(yarrow 0)[ (f)_(y)(0,y)-(f)_(y)(0,0)] =0

下面二次型中正定的是( ）。A. f(x_(1),x_(2),x_(3))=x_(1)^2+x_(2)^2；B. f(x_(1),x_(2),x_(3))=x_(1)^2+x_(2)^2+2x_(1)x_(2)+6x_(3)^2；C. f(x_(1),x_(2),x_(3))=4x_(1)^2+3x_(2)^2+6x_(3)^2-x_(1)x_(2)-x_(1)x_(3)；D. f(x_(1),x_(2),x_(3))=x_(1)^2+x_(2)^2+x_(3)^2+2x_(1)x_(2)+2x_(1)x_(3)+2x_(2)x_(3)；

选用优先数系时应遵循的规则是先疏后密的原则。A. 对B. 错

如图所示 线性方程组 ) x+y+z=0 2x-5y-3z=10 4x+8y+2z=4 . 的解为

已知9^m=10，a=10^m-11，b=8^m-9，则(  )。A. a>0>bB. a>b>0C. b>a>0D. b>0>a

设函数f（x）的定义域为R，f（x+1）为奇函数，f（x+2）为偶函数，当x∈[1，2]时，f（x）=ax2+b．若f（0）+f（3）=6，则f（(9)/(2)）=（ ）A. -(9)/(4)B. -(3)/(2)C. (7)/(4)D. (5)/(2)

在△ABC中，cosC=(2)/(3)，AC=4，BC=3，则cosB=（ ）A. (1)/(9)B. (1)/(3)C. (1)/(2)D. (2)/(3)

2. 某工厂有三个车间A,B,C,生产一种产品的概率依次为0.6, 0.3, 0.1,它-|||-们的次品率依次为0.01,0.05,0.04。若从这批产品中随机取一件,求该产-|||-品是次品的概率?

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