The curve C has equation, y= 9 - 4x - \frac{8}{x}. The point P on C has x-coordinate equal to 2.

The tangent at P meets the x-axis at A and the normal at P meets the x-axis at B.
a) Find the area of triangle APB.
The tangent at P meets the x-axis at A and the normal at P meets the x-axis at B.
a) Find the area of triangle APB.
Step 1: Calculate the point P(any variable) on the curve
NOTE: Substitute the given coordinate in the curve equation to get the
point
EXAMPLE: y = 9 - 4x - \frac{8}{x}, x-coordinate = 2
So, y = 9 - 4*2 - \frac{8}{2}
y = 9 - 8 - 4 = -3
Step 1: Calculate the slope of the curve
Skill 1: Note down the given curve equation and apply the differentiation on
both sides
NOTE: Multiple both sides of the function by \frac{dy}{dx}
Skill 2: Differentiate both sides of the function with respect
to x (any variable).
EXAMPLE: y = x^3 - 2x^2 - x + 9
[math] \frac{d}{dx} y = \frac{d}{dx}[x^3] - \frac{d}{dx} [2x^2] -\frac{d}{dx} x + \frac{d}{dx} 9][/math]
\frac{dy}{dx} = 3x^2 - 4x - 1
Skill 3: Plug in the (x, y) values to find ( \frac{dy}{dx})
for that point.
Skill 4: To know the slope (gradient), apply the BODMAS rules to simplify
the equation.
Step 2: Find the equation of tangent line and the point
Skill 1: Use the slope of curve and a point on curve to find its y-intercept.
NOTE:
Skill 2: Use the slope of line and the y-intercept of line to find the equation
of the line.
EXAMPLE: Plug the slope m = -2 and the y-intercept b = -8 into the
slope- intercept formula.
y = mx + b
y = -2x + -8
Step 3: Find the equation of the normal line to the tangent
NOTE: i) Repeat the step 2 but change the slope.
ii) Perpendicular lines have slopes that are opposite
reciprocals, like \frac{a}{b} \text{ and } \frac{-b}{a}. The slopes also have a product of -1
Step 4: Skill 3: Substitute the corresponding intercept of above lines, to get required point.
NOTE: i) If the line intersects with the x-axis put y = 0 then simplify for the x-coordinator
ii)If the line intersects with the y-axis put x = 0 then simplify for the y-coordinator
Step 5: Calculate the area of the triangle
Method 1:
Step 1: Locate the coordinates of the endpoints.
EXAMPLE: The given points M (2, 3) and N (-1, 0), (2, -4.)
Therefore, (x_1, y_1) = (2, 3),(x_2, y_2) = (-1, 0) and (x_3, y_3) = (2, -4).
Step 2: Plug the corresponding coordinates into the Area of triangle formula
FORMULA:
Area of the triangle
\frac{1}{2} {x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2)}
Step 3: Simplify further
NOTE: Apply the BODMAS rules
Method 2:
Step 1: Calculate the base and height lengths of the triangle
NOTE: Use the distance formula to calculate lengths.
Step 2: Substitute the either values (base and height lengths) in the formula
Area of the right angle triangle = \frac{1}{2} base * height
Step 3: Simplify further
NOTE: Apply the BODMAS rules