Find approximations to the value of:

$\displaystyle \int_{1}^5 \frac{1}{x^2} dx$

Using the trapezium rule with 4 intervals.

Now I know that it's calculated using the formula:

$\displaystyle \frac{h}{2} (f(x_{0}) + f(x_{n})) + 2(f(x_{1}) + f(x_{2}) ... f(x_{n-1}))$ Where:

n = interval

$\displaystyle h = \frac {b - a}{n}$

$\displaystyle x_{k} = a + kh$

But the answer is not coming right :

= 1/2 (1 + 1/25) + 2(1/4 + 1/9 + 1/16)