趣味的数学-179
√65 - √63最接近下列哪个小数？
A】0.12
B】0.13
C】0.14
D】0.15
E】0.16
√65 = √(64+1) = 8 √(1+1/64)
√63 = √(64-1) = 8 √(1-1/64)
√(1+x) = 1+1/2 *x - 1/8 * x^2 +1/16*x^3.....
√(1-x) = 1-1/2 *x - 1/8 * x^2 -1/16*x^3.....
x = 1/64
√65 - √63 = 8*(x + 1/8 *x^3 +....) = 1/8 + ... >0.125
