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lim(h→0)[f(a+h)+f(a-h)-2f(a)]/h^2(设f^"(x)在x=a点邻近连续

题目详情
lim(h→0)[f(a+h)+f(a-h)-2f(a)]/h^2(设f^"(x)在x=a点邻近连续
▼优质解答
答案和解析
f(a+h)=f(a)+f'(a)h+0.5f''(θ1)h^2f(a-h)=f(a) -f'(a)h+0.5f''(θ2)h^2∴ lim(h→0)[f(a+h)+f(a-h)-2f(a)]/h^2=lim(h→0)[0.5f''(θ1)+0.5f''(θ2)]=f''(a)这是因为f^"(x)在x=a点邻近连续.