Question

The point P(5, −4) lies on the curve y = 4/(4 − x).
(a) If Q is the point (x, 4/(4 − x)), use your calculator to find the slope m_PQ of the secant line PQ (correct to six decimal places) for the following values of x.

(i) 4.9
(ii) 4.99
(iii) 4.999
(iv) 4.9999
(v) 5.1
(vi) 5.01
(vii) 5.001
(viii) 5.0001

(b) Using the results of part (a), guess the value of the slope m of the tangent line to the curve at P(5, −4).

Answer 1

Answer:

4

Step-by-step explanation:

Slope refers to the steepness of the line.

Slope is equal to change in value of y divided by change in value of x.

The slope of the secant line is given by $\frac{f(x)-f(a)}{x-a}$.

Given points are $P\left ( 5,-4 \right )\,,\,Q\left ( x,\frac{4}{4-x} \right )$

So, slope of the secant line is $\frac{\frac{4}{4-x}+4}{x-5}=\frac{4+4(4-x)}{(x-5)(4-x)}=\frac{20-4x}{(x-5)(4-x)}=\frac{-4(x-5)}{(x-5)(4-x)}=\frac{-4}{4-x}=\frac{4}{x-4}$

(i) At x = 4.9,

$\frac{4}{4.9-4}=\frac{4}{0.9}=4.444444$

(ii) At x = 4.99,

$\frac{4}{4.99-4}=\frac{4}{0.99}=4.040404$

(iii) At x = 4.999,

$\frac{4}{4.999-4}=\frac{4}{0.999}=4.004004$

(iv) At x = 4.9999,

$\frac{4}{4.9999-4}=\frac{4}{0.9999}=4.0004$

(v) At x =5.1,

$\frac{4}{5.1-4}=\frac{4}{1.1}=3.636364$

(vi)

At x = 5.01,

$\frac{4}{5.01-4}=\frac{4}{1.01}=3.960396$

(vii) At x = 5.001,

$\frac{4}{5.001-4}=\frac{4}{1.001}=3.996004$

(viii) At x = 5.0001,

$\frac{4}{5.0001-4}=\frac{4}{1.0001}=3.9996$

(b)

Slope of the tangent line is 4.