Photo AI

7 (a) Express \( \frac{4x+3}{(x-1)^2} \) in the form \( \frac{A}{x-1} + \frac{B}{(x-1)^2} \) - AQA - A-Level Maths Pure - Question 7 - 2019 - Paper 3

Question icon

Question 7

7-(a)-Express-\(-\frac{4x+3}{(x-1)^2}-\)-in-the-form-\(-\frac{A}{x-1}-+-\frac{B}{(x-1)^2}-\)-AQA-A-Level Maths Pure-Question 7-2019-Paper 3.png

7 (a) Express \( \frac{4x+3}{(x-1)^2} \) in the form \( \frac{A}{x-1} + \frac{B}{(x-1)^2} \). 7 (b) Show that \( \int_{3}^{4} \frac{4x+3}{(x-1)^2} dx = p + \ln q \)... show full transcript

Worked Solution & Example Answer:7 (a) Express \( \frac{4x+3}{(x-1)^2} \) in the form \( \frac{A}{x-1} + \frac{B}{(x-1)^2} \) - AQA - A-Level Maths Pure - Question 7 - 2019 - Paper 3

Step 1

Express \( \frac{4x+3}{(x-1)^2} \) in the form \( \frac{A}{x-1} + \frac{B}{(x-1)^2} \)

96%

114 rated

Answer

To express ( \frac{4x+3}{(x-1)^2} ) in the required form, start with:

4x+3(x1)2=Ax1+B(x1)2\frac{4x+3}{(x-1)^2} = \frac{A}{x-1} + \frac{B}{(x-1)^2}

Multiply through by ( (x-1)^2 ):

4x+3=A(x1)+B4x + 3 = A(x-1) + B

Now, setting ( x = 1 ) will eliminate ( A ):

4(1)+3=BB=74(1) + 3 = B \Rightarrow B = 7

Next, we can differentiate the equation:

4=A4 = A.

Thus, we have ( A = 4 ) and ( B = 7 ).

Step 2

Show that \( \int_{3}^{4} \frac{4x+3}{(x-1)^2} dx = p + \ln q \)

99%

104 rated

Answer

Integrate ( \frac{4x+3}{(x-1)^2} ):

Using the earlier expression, we can integrate:

4x1+7(x1)2dx\int \frac{4}{x-1} + \frac{7}{(x-1)^2} dx

This gives:

4x1dx+7(x1)2dx=4lnx17x1+C\int \frac{4}{x-1} dx + \int \frac{7}{(x-1)^2} dx = 4\ln |x-1| - \frac{7}{x-1} + C

Evaluating from 3 to 4:

[4ln41741][4ln31731]\left[ 4\ln |4-1| - \frac{7}{4-1} \right] - \left[ 4\ln |3-1| - \frac{7}{3-1} \right]

Substituting values, we get:

=4ln373(4ln272)= 4\ln 3 - \frac{7}{3} - (4\ln 2 - \frac{7}{2})

Combining terms gives us:

=4ln(32)+7273= 4\ln(\frac{3}{2}) + \frac{7}{2} - \frac{7}{3}.

By simplifying further, this shows the required form ( p + \ln q ).

Join the A-Level students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;