Can l have any notes on how to calculate frequency density and accumulated density equation of the line gradient area under the graph and so on

Here are some notes on the concepts you asked about:

Frequency Density
Frequency density is used to plot histograms when class intervals are not equal. It represents the frequency per unit of the class interval.

$$\text{Frequency Density} = \frac{\text{Frequency}}{\text{Class Width}}$$

The height of a bar in a histogram is its frequency density, and the area of the bar represents the frequency of that class.

Accumulated Density (Cumulative Frequency Density)
Accumulated density, often referred to as cumulative frequency density, is not a standard term. However, cumulative frequency is the running total of frequencies. A cumulative frequency graph (ogive) plots cumulative frequency against the upper class boundary. The "density" aspect usually refers to probability density functions in continuous distributions, where the cumulative distribution function (CDF) gives the probability that a random variable takes a value less than or equal to a certain value.
For a continuous variable with probability density function $f(x)$, the cumulative distribution function $F(x)$ is:

$$F(x) = P(X \le x) = \int_{-\infty}^{x} f(t)\,dt$$

Equation of the Line
The equation of a straight line describes the relationship between the $x$ and $y$ coordinates of all points on the line.
The most common form is the slope-intercept form:

$$y = mx + c$$

where $m$ is the gradient (slope) and $c$ is the $y$-intercept (the point where the line crosses the $y$-axis).
Another form is the point-slope form:

$$y - y_1 = m(x - x_1)$$

where $m$ is the gradient and $(x_1, y_1)$ is a known point on the line.

Gradient of a Line
The gradient (or slope) of a line measures its steepness. It is the ratio of the vertical change (rise) to the horizontal change (run) between any two points on the line.
Given two points $(x_1, y_1)$ and $(x_2, y_2)$, the gradient $m$ is:

$$m = \frac{\text{Change in } y}{\text{Change in } x} = \frac{y_2 - y_1}{x_2 - x_1}$$

A positive gradient indicates an upward slope, a negative gradient indicates a downward slope, a zero gradient is a horizontal line, and an undefined gradient is a vertical line.

Area Under the Graph
The area under a graph represents the accumulation of the quantity plotted on the vertical axis with respect to the quantity plotted on the horizontal axis.
For simple shapes (like rectangles, triangles, trapezoids), the area can be calculated using geometric formulas.
For more complex curves, the area under the graph of a function $f(x)$ from $x=a$ to $x=b$ is given by the definite integral:

$$\text{Area} = \int_{a}^{b} f(x)\,dx$$

This integral calculates the signed area, meaning areas below the x-axis are considered negative.