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Question: A B + 3х – 2 . a) Find A and B where (x + 3)(2x - 1) b) Evaluate the integral x + 3 2x - 1 3x – 2 dx. (x+3)(2x – 1)

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Answer: the original integral is:

∫ (3x - 2) / (x - 3)(2x - 1) dx = (7/5)ln|x - 3| + (1/10)ln|2x - 1| + C

Step-by-step explanation:In order to solve for A and B, we need to expand the expression (x - 3)(2x - 1):

(x - 3)(2x - 1) = 2x^2 - x - 6x + 3

= 2x^2 - 7x + 3

Now, we equate the coefficients of like terms:

2x^2 - 7x + 3 = A(3x - 2)

Comparing the x^2 coefficients:

2 = 3A

A = 2/3

Comparing the x coefficients:

-7 = -2A

-7 = -2(2/3)

-7 = -4/3

-7 = B

Therefore, A = 2/3 and B = -7.

Now, let's evaluate the integral ∫ (3x - 2) / (x - 3)(2x - 1) dx:

We can start by performing a partial fractions decomposition:

(3x - 2) / (x - 3)(2x - 1) = A / (x - 3) + B / (2x - 1)

Multiplying both sides by (x - 3)(2x - 1), we get:

(3x - 2) = A(2x - 1) + B(x - 3)

Expanding and equating coefficients, we have:

3x - 2 = (2A + B)x - (A + 3B)

Equate the x coefficients:

3 = 2A + B

Equate the constant terms:

-2 = -A - 3B

Now we can solve these equations simultaneously:

From the first equation, we can solve for B:

B = 3 - 2A

Substituting into the second equation:

-2 = -A - 3(3 - 2A)

-2 = -A - 9 + 6A

-2 = 5A - 9

7 = 5A

A = 7/5

Substituting the value of A back into the equation for B:

B = 3 - 2(7/5)

B = 3 - 14/5

B = (15 - 14) / 5

B = 1/5

Therefore, A = 7/5 and B = 1/5.

Now we can rewrite the integral:

∫ (3x - 2) / (x - 3)(2x - 1) dx = ∫ (7/5)/(x - 3) dx + ∫ (1/5)/(2x - 1) dx

To integrate the first term, we use the natural logarithm function:

∫ (7/5)/(x - 3) dx = (7/5)ln|x - 3| + C

To integrate the second term, we use another substitution:

Let u = 2x - 1.

Then, du = 2dx, or dx = (1/2)du.

The integral becomes:

∫ (1/5)/(2x - 1) dx = ∫ (1/5)/u (1/2) du

= (1/10)ln|u| + C

= (1/10)ln|2x - 1| + C

Therefore, the original integral is:

∫ (3x - 2) / (x - 3)(2x - 1) dx = (7/5)ln|x - 3| + (1/10)ln|2x - 1| + C

i hope I'm right

User Cosmin SD
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