现代数值数学和计算习题答案(同济版)(5)

functions=nrmv(x)x=abs(x(x~=0));n=length(x);ifn==0,

s=0;elseifn==1,

s=abs(x);else

scale=0;ssq=1;forj=1:n,

if(scale<x(j)),

ssq=1+ssq*(scale/x(j))^2;scale=x(j);else

ssq=ssq+(x(j)/scale)^2;endend

s=scale*sqrt(ssq);end

BLAS

dnrm2

http://www.77cn.com.cn/blas/dnrm2.f.

8.

ax2√

+bx+x=0

x= b±2a

x=2ca=0cb2= 0

4ac

.a

c10

6e+154

-4e+154

1

1

1

-4

-1e155

1e+155

5

MatLab