更多"If x and y are integers, is xy+1 di"的相关试题:
[单项选择]If x and y are positive integers and x is a multiple of y，is y=2 ？（）
(1)y≠1
(2)x+2 is a multiple of y.
A. 条件(1)充分，但条件(2)不充分．
B. 条件(2)充分，但条件(1)不充分．
C. 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
D. 条件(1)充分，条件(2)也充分．
E. 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
[单项选择]If x and y are integers such that x3 = y2, which of the following could not be the value of y
A. -1
B. 1
C. 8
D. 16
E. 27
[单项选择]If x, y, and z are positive integers and 3x=4y=7z, then the least possible value of x+y+z is （）
A. 33
B. 40
C. 49
D. 61
E. 84
[单项选择]If x, y, and z are positive integers, and 4x=5y=6z, then the least possible value of x+y+z is （）.
A. 15
B. 28
C. 37
D. 42
E. 6O
[单项选择]If x and y are integers and xy=5, then (x+y)2=（）。
A. 13
B. 16
C. 25
D. 26
E. 36
[单项选择]If x, y, and z are single-digit integers and 100(x)+1,000(y)+10(z)=N, what is the units' digit of the number N ？（）
A. 0
B. 1
C. x
D. y
E. z
[单项选择]If k and n are integers, is n divisible by 7 （）
(1)n-3=2k
(2)2k-4 is divisible by 7.
A. 条件(1)充分，但条件(2)不充分．
B. 条件(2)充分，但条件(1)不充分．
C. 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
D. 条件(1)充分，条件(2)也充分．
E. 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
[单项选择]If the product of the integers ω, x, y, and z is 770, and if 1＜ω＜z＜y＜z, what is the value of ω+z ？（）
A. 10
B. 13
C. 16
D. 18
E. 21
[单项选择]If ω, x, y, and z are non-negative integers, each less than 3, and ω(33)+x(32)+y(3)+z=34，thenω+z=（）。
A. 0
B. 1
C. 2
D. 3
E. 4
[单项选择]设f(x，x2)=x2e-x，y'x(x，y)|y=x2=-x2e-x(x＞0)，则f'y(x，y)|y=x2等于
A. 2xe-x
B. (-x2+2x)e-x
C. e-x
D. (2x-1)e-x
[单项选择]设f(x，y)与φ(x，y)均为可微函数，且φ'y(x，y)≠0，已知(x0，y0)是f(x，y)在约束条件φ(x，y)=0下的一个极值点，下列选项正确的是
[单项选择]二元函数f(x，y)在点(x0，y0)处的两个偏导数f'x(x，y)，f'y(x，y)连续是f(x，y)在该点可微的
A. 必要条件而非充分条件．
B. 充分条件而非必要条件．
C. 充分必要条件．
D. 既非必要条件又非充分条件．
[单项选择]设y1(x)，y2(x)，y3(x)是二阶线性非齐次微分方程y"+p(x)y'+q(x)y=f(x)的三个线性无关解，C1，C2是任意常数，则此微分方程的通解是
A. C1y1+C2y2+y3．
B. C1y1+C2y2+(1-C1-C2)y3．
C. C1y1+C2y2-(C1+C2)y3．
D. C1y1+C2y2-(1-C1-C2)y3．
