用钢尺往返丈量120m的距离,要求相对误差达到1/10000,则往返校差不得大于()m。
A.0.048
B.0.012
C.0.024
D.0.036
参考答案:B
解析:
The goals of language instruction in the 1960s were on the oral medium, and ______ was deemphasized.
设有n元实二次型
f(x1,x2,…xn)=(x1+a1x2)2+(x2+a2x3)2+…+(xn-1+an-1xn)2+(xn+anx1)2,其中ai(i=1,2,…,n)为实数.试问:当a1,a2,…an满足何种条件时,二次型f(x1,x2,…xn)为正定二次型.