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Solve the following absolute value inequalities and partial fractions: |5x+4| ext<= 1, |5x-7| > 2, and resolve rac6x-9(x-3)(x-2) into partial fractions.

Mathematics

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B

Step-by-step solution

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Here are the solutions to the problems:

49. Solve ∣5x+4∣≤1|5x+4| \le 1.

  1. Rewrite the absolute value inequality.

    −1≤5x+4≤1-1 \le 5x+4 \le 1
  2. Subtract 4 from all parts of the inequality.

    −1−4≤5x≤1−4-1 - 4 \le 5x \le 1 - 4 −5≤5x≤−3-5 \le 5x \le -3
  3. Divide all parts by 5.

    −55≤x≤−35\frac{-5}{5} \le x \le \frac{-3}{5} −1≤x≤−35-1 \le x \le -\frac{3}{5}
  4. Express the solution in interval notation.

    x∈[−1,−35]x \in \left[-1, -\frac{3}{5}\right]

    The correct option is B.

    50. Solve ∣5x−7∣>2|5x-7| > 2.

  5. Rewrite the absolute value inequality as two separate inequalities.

    5x−7>2or5x−7<−25x-7 > 2 \quad \text{or} \quad 5x-7 < -2
  6. Solve the first inequality.

    5x−7>25x-7 > 2 5x>2+75x > 2+7 5x>95x > 9 x>95x > \frac{9}{5}
  7. Solve the second inequality.

    5x−7<−25x-7 < -2 5x<−2+75x < -2+7 5x<55x < 5 x<55x < \frac{5}{5} x<1x < 1
  8. Combine the solutions and express in interval notation.

    x∈(−∞,1)∪(95,∞)x \in (-\infty, 1) \cup \left(\frac{9}{5}, \infty\right)

    The correct option is B.

    51. Resolve 6x−9(x−3)(x−2)\frac{6x-9}{(x-3)(x-2)} into partial fractions.

  9. Set up the partial fraction decomposition.

    6x−9(x−3)(x−2)=Ax−3+Bx−2\frac{6x-9}{(x-3)(x-2)} = \frac{A}{x-3} + \frac{B}{x-2}
  10. Multiply both sides by (x−3)(x−2)(x-3)(x-2).

    6x−9=A(x−2)+B(x−3)6x-9 = A(x-2) + B(x-3)
  11. Solve for A and B.

    Let x=2x=2:

    6(2)−9=A(2−2)+B(2−3)6(2)-9 = A(2-2) + B(2-3) 12−9=0+B(−1)12-9 = 0 + B(-1) 3=−B  ⟹  B=−33 = -B \implies B = -3

    Let x=3x=3:

    6(3)−9=A(3−2)+B(3−3)6(3)-9 = A(3-2) + B(3-3) 18−9=A(1)+018-9 = A(1) + 0 9=A9 = A
  12. Substitute A and B back into the decomposition.

    6x−9(x−3)(x−2)=9x−3+−3x−2\frac{6x-9}{(x-3)(x-2)} = \frac{9}{x-3} + \frac{-3}{x-2} 6x−9(x−3)(x−2)=9x−3−3x−2\frac{6x-9}{(x-3)(x-2)} = \frac{9}{x-3} - \frac{3}{x-2}

    The correct option is B.

    52. Resolve 8x+4x2−4\frac{8x+4}{x^2-4} into partial fractions.

  13. Factor the denominator.

    x2−4=(x−2)(x+2)x^2-4 = (x-2)(x+2)
  14. Set up the partial fraction decomposition.

    8x+4(x−2)(x+2)=Ax−2+Bx+2\frac{8x+4}{(x-2)(x+2)} = \frac{A}{x-2} + \frac{B}{x+2}
  15. Multiply both sides by (x−2)(x+2)(x-2)(x+2).

    8x+4=A(x+2)+B(x−2)8x+4 = A(x+2) + B(x-2)
  16. Solve for A and B.

    Let x=2x=2:

    8(2)+4=A(2+2)+B(2−2)8(2)+4 = A(2+2) + B(2-2) 16+4=A(4)+016+4 = A(4) + 0 20=4A  ⟹  A=520 = 4A \implies A = 5

    Let x=−2x=-2:

    8(−2)+4=A(−2+2)+B(−2−2)8(-2)+4 = A(-2+2) + B(-2-2) −16+4=0+B(−4)-16+4 = 0 + B(-4) −12=−4B  ⟹  B=3-12 = -4B \implies B = 3
  17. Substitute A and B back into the decomposition.

    8x+4x2−4=5x−2+3x+2\frac{8x+4}{x^2-4} = \frac{5}{x-2} + \frac{3}{x+2}

    The correct option is B.

    53. Find the general term Tr+1T_{r+1} of the binomial expansion of (2x+1x)8\left(2x + \frac{1}{x}\right)^8.

  18. Use the binomial theorem formula for the (r+1)(r+1)-th term

    Tr+1=(nr)an−rbrT_{r+1} = \binom{n}{r} a^{n-r} b^r.
    Here, n=8n=8, a=2xa=2x, and b=1xb=\frac{1}{x}.

  19. Substitute the values into the formula.

    Tr+1=(8r)(2x)8−r(1x)rT_{r+1} = \binom{8}{r} (2x)^{8-r} \left(\frac{1}{x}\right)^r
  20. Simplify the expression.

    Tr+1=(8r)28−rx8−rx−rT_{r+1} = \binom{8}{r} 2^{8-r} x^{8-r} x^{-r} Tr+1=(8r)28−rx8−r−rT_{r+1} = \binom{8}{r} 2^{8-r} x^{8-r-r} Tr+1=(8r)28−rx8−2rT_{r+1} = \binom{8}{r} 2^{8-r} x^{8-2r}

    The correct option is B.

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