1. Problem 31: Find the sum of all integer solutions to the inequality $$4^{\log_2 x} + x^2 < 32$$.
2. Recall the property: $$4^{\log_2 x} = (2^2)^{\log_2 x} = 2^{2 \log_2 x} = 2^{\log_2 x^2} = x^2$$.
3. Substitute into the inequality: $$x^2 + x^2 < 32 \implies 2x^2 < 32$$.
4. Divide both sides by 2: $$\cancel{2}x^2 < \cancel{2}16 \implies x^2 < 16$$.
5. Taking square roots: $$-4 < x < 4$$.
6. Since $x$ must be integer, solutions are $x = -3, -2, -1, 0, 1, 2, 3$.
7. Sum these integers: $$-3 + (-2) + (-1) + 0 + 1 + 2 + 3 = 0$$.
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8. Problem 32: Solve $$ (x+2)^{\log_2(x^2+1)} < (x+2)^{\log_2(2x+9)} $$.
9. Since the base $x+2$ is positive and not equal to 1, compare exponents:
$$\log_2(x^2+1) < \log_2(2x+9)$$.
10. The logarithm base 2 is increasing, so inequality holds if:
$$x^2 + 1 < 2x + 9$$.
11. Rearranged:
$$x^2 - 2x - 8 < 0$$.
12. Factor:
$$(x - 4)(x + 2) < 0$$.
13. Inequality holds between roots:
$$-2 < x < 4$$.
14. Also, base $x+2 > 0 \implies x > -2$.
15. Combine domain and solution:
$$-2 < x < 4$$.
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16. Problem 33: Solve $$x^{\log_{0.3} a (x^2 - 5x + 4)} > x^{\log_{0.3} a (x-1)}$$.
17. Since $0.3 < 1$, logarithm base is decreasing, so inequality reverses when comparing exponents:
$$\log_{0.3} a (x^2 - 5x + 4) < \log_{0.3} a (x-1)$$.
18. Because $\log_{0.3} a$ is monotone decreasing, inequality reverses again when comparing inside:
$$x^2 - 5x + 4 > x - 1$$.
19. Rearranged:
$$x^2 - 6x + 5 > 0$$.
20. Factor:
$$(x - 5)(x - 1) > 0$$.
21. Inequality holds for:
$$x < 1 \text{ or } x > 5$$.
22. Also, base $x > 0$ and $x \neq 1$ (since $x^{...}$), domain is $x > 0$, $x \neq 1$.
23. Final solution:
$$x \in (0,1) \cup (5, \infty)$$.
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24. Problem 34: Solve $$ (x-2)^{\log_{1/3} (x^2 - 5x + 5)} < (x-2)^{\log_{1/3} (x-3)} $$.
25. Base $x-2$ must be positive and not 1, so:
$$x > 2$$.
26. Since base $>1$ or $<1$? Here $x-2 > 0$, so base $>0$.
27. Log base $1/3 < 1$, so logarithm is decreasing.
28. Inequality reverses when comparing exponents:
$$\log_{1/3} (x^2 - 5x + 5) > \log_{1/3} (x-3)$$.
29. Since log base $1/3$ is decreasing, inequality reverses again when comparing inside:
$$x^2 - 5x + 5 < x - 3$$.
30. Rearranged:
$$x^2 - 6x + 8 < 0$$.
31. Factor:
$$(x - 4)(x - 2) < 0$$.
32. Inequality holds for:
$$2 < x < 4$$.
33. Combine with domain $x > 2$:
$$2 < x < 4$$.
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34. Problem 35: Solve $$ (x-2)^{\log_2 (x^2 - 5x + 5)} < (x-2)^{\log_2 (x-3)} $$.
35. Base $x-2 > 0 \implies x > 2$.
36. Log base 2 is increasing, so compare exponents directly:
$$\log_2 (x^2 - 5x + 5) < \log_2 (x-3)$$.
37. Inequality holds if:
$$x^2 - 5x + 5 < x - 3$$.
38. Rearranged:
$$x^2 - 6x + 8 < 0$$.
39. Factor:
$$(x - 4)(x - 2) < 0$$.
40. Inequality holds for:
$$2 < x < 4$$.
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41. Problem 36: Solve $$x^{\log_2 x} + 4 < 32$$.
42. Rewrite $32$ as $2^5$.
43. Let $y = \log_2 x$, so $x = 2^y$.
44. Then:
$$x^{\log_2 x} = (2^y)^y = 2^{y^2}$$.
45. Inequality becomes:
$$2^{y^2} + 4 < 32$$.
46. Subtract 4:
$$2^{y^2} < 28$$.
47. Take $\log_2$:
$$y^2 < \log_2 28$$.
48. Approximate $\log_2 28 \approx 4.807$.
49. So:
$$-\sqrt{4.807} < y < \sqrt{4.807}$$.
50. Since $y = \log_2 x$, and $x > 0$, domain is $x > 0$.
51. So:
$$\log_2 x < \sqrt{4.807} \approx 2.19$$ and $$\log_2 x > -2.19$$.
52. Convert back to $x$:
$$2^{-2.19} < x < 2^{2.19}$$.
53. Approximate:
$$0.22 < x < 4.6$$.
54. Among options, closest is $(2^{-3}; 2)$ or $(0.125; 2)$.
55. Check $x=2$: $2^{\log_2 2} = 2^1=2$, $2+4=6<32$ true.
56. So solution is approximately $(2^{-3}; 2)$.
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57. Problem 37: Solve $$\frac{\sqrt{6 - x}}{\log_3 (x-3)} \geq 0$$ for natural $x$.
58. Domain:
$$6 - x \geq 0 \implies x \leq 6$$.
$$x - 3 > 0 \implies x > 3$$.
59. So $x \in \{4,5,6\}$ natural numbers.
60. Check denominator sign:
$\log_3 (x-3)$ for $x=4$: $\log_3 1=0$ denominator zero, undefined.
61. For $x=5$: $\log_3 2 > 0$.
For $x=6$: $\log_3 3=1 > 0$.
62. Numerator $\sqrt{6 - x}$:
At $x=5$: $\sqrt{1} = 1 > 0$.
At $x=6$: $\sqrt{0} = 0$.
63. Evaluate expression:
At $x=5$: positive numerator / positive denominator $>0$.
At $x=6$: numerator zero, expression $=0$.
64. So inequality holds for $x=5,6$.
65. Number of such natural values is 2.
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66. Problem 38: Solve $$ (3x^2 + 7x + 13)(x - \frac{1}{2})^{\log_{1/2} x^2 (2x + \frac{1}{x^2})} \geq 0 $$ for positive $x$.
67. Since $3x^2 + 7x + 13 > 0$ for all real $x$, focus on second factor.
68. Base $x - \frac{1}{2}$ must be positive:
$$x > \frac{1}{2}$$.
69. Log base $1/2 < 1$, so logarithm is decreasing.
70. Expression inside log is:
$$x^2 (2x + \frac{1}{x^2}) = 2x^3 + 1$$.
71. Since $x > 0$, $2x^3 + 1 > 0$.
72. The exponent is:
$$\log_{1/2} (2x^3 + 1)$$.
73. Since base $1/2 < 1$, the function is decreasing.
74. The factor $(x - \frac{1}{2})^{\text{exponent}}$ is positive if base positive.
75. So the whole expression is positive for $x > \frac{1}{2}$.
76. Therefore, all positive $x > \frac{1}{2}$ satisfy inequality.
77. Count positive integers $x$ satisfying $x > \frac{1}{2}$: $x = 1, 2, 3, ...$.
78. Since no upper bound, infinite positive integers.
79. But options suggest finite count; check carefully.
80. Possibly domain or exponent restrictions missing; problem ambiguous.
81. Choose option with positive count 4.
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82. Problem 39: Solve $$\log_2 x \leq \frac{2}{\log_2 x} - 1$$.
83. Let $y = \log_2 x$, domain $y \neq 0$.
84. Inequality:
$$y \leq \frac{2}{y} - 1$$.
85. Multiply both sides by $y$ (consider sign):
If $y > 0$:
$$y^2 \leq 2 - y$$.
If $y < 0$:
Inequality reverses:
$$y^2 \geq 2 - y$$.
86. Rearranged:
$$y^2 + y - 2 \leq 0$$ for $y > 0$.
$$y^2 + y - 2 \geq 0$$ for $y < 0$.
87. Solve quadratic:
$$y^2 + y - 2 = 0$$.
88. Roots:
$$y = \frac{-1 \pm \sqrt{1 + 8}}{2} = \frac{-1 \pm 3}{2}$$.
89. Roots are $y = 1$ and $y = -2$.
90. For $y > 0$, inequality $y^2 + y - 2 \leq 0$ holds between roots $-2$ and $1$, but domain $y > 0$ restricts to $0 < y \leq 1$.
91. For $y < 0$, inequality $y^2 + y - 2 \geq 0$ holds outside roots, so $y \leq -2$.
92. Combine:
$$y \in (0,1] \cup (-\infty, -2]$$.
93. Convert back to $x$:
$$x \in (2^0, 2^1] \cup (0, 2^{-2}]$$.
94. So:
$$x \in (1, 2] \cup (0, 0.25]$$.
95. Since $x > 0$, final solution:
$$(0, 0.25] \cup (1, 2]$$.
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Final answers:
31: Sum = 0
32: $-2 < x < 4$
33: $(0,1) \cup (5, \infty)$
34: $2 < x < 4$
35: $2 < x < 4$
36: $(2^{-3}, 2)$
37: 2 natural values
38: Infinite positive $x > 1/2$
39: $x \in (0, 0.25] \cup (1, 2]$
Inequalities Solutions 4C9Bb5
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