Problem Analysis #31

Solar-Pro-2 (31B)(high) · Run 1

35.01s
7,096 toks
Problem Statement

For all real numbers xx with 2x2-2 \leq x \leq 2, the inequality

k2x3+3x212x8k-k \leq 2x^3 + 3x^2 - 12x - 8 \leq k

holds. Find the smallest possible positive value of kk. [3 points]\

Ground Truth
15
Execution Trace
Reasoning Process

[THOUGHT] To find the smallest positive value of kk such that the inequality k2x3+3x212x8k-k \leq 2x^3 + 3x^2 - 12x - 8 \leq k holds for all xx in the interval [2,2][-2, 2], we need to determine the maximum absolute value of the function f(x)=2x3+3x212x8f(x) = 2x^3 + 3x^2 - 12x - 8 on this interval. This involves evaluating f(x)f(x) at the critical points and the endpoints of the interval.

First, we find the critical points by setting the derivative f(x)f'(x) to zero:

f(x)=6x2+6x12=0f'(x) = 6x^2 + 6x - 12 = 0

Solving this quadratic equation, we get:

x2+x2=0    (x+2)(x1)=0    x=2 or x=1x^2 + x - 2 = 0 \implies (x + 2)(x - 1) = 0 \implies x = -2 \text{ or } x = 1

The critical points are x=2x = -2 and x=1x = 1. Since x=2x = -2 is an endpoint, we only need to consider x=1x = 1 as an internal critical point. We evaluate f(x)f(x) at the endpoints x=2x = -2, x=2x = 2, and the critical point x=1x = 1.

Next, we compute the function values at these points:

f(2)=2(2)3+3(2)212(2)8=16+12+248=12f(-2) = 2(-2)^3 + 3(-2)^2 - 12(-2) - 8 = -16 + 12 + 24 - 8 = 12 f(1)=2(1)3+3(1)212(1)8=2+3128=15f(1) = 2(1)^3 + 3(1)^2 - 12(1) - 8 = 2 + 3 - 12 - 8 = -15 f(2)=2(2)3+3(2)212(2)8=16+12248=4f(2) = 2(2)^3 + 3(2)^2 - 12(2) - 8 = 16 + 12 - 24 - 8 = -4

The absolute values of these function values are:

f(2)=12,f(1)=15,f(2)=4|f(-2)| = 12, \quad |f(1)| = 15, \quad |f(2)| = 4

The maximum absolute value is 15, which occurs at x=1x = 1. Therefore, the smallest possible positive value of kk is 15.

To confirm, we can use Python to evaluate the function at these points and verify the maximum absolute value. [/THOUGHT]

[PYTHON] def f(x): return 2x**3 + 3x**2 - 12*x - 8

Evaluate the function at the critical points and endpoints

points = [-2, 1, 2] values = [f(x) for x in points] abs_values = [abs(v) for v in values] max_abs = max(abs_values) print(max_abs) [/PYTHON]

Tool Output
[PYTHON OUTPUT] 15 [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] The Python output confirms that the maximum absolute value of the function on the interval [2,2][-2, 2] is 15. Therefore, the smallest possible positive value of kk is 15. [/THOUGHT] 15\boxed{15}

Final Model Output
15

Comparative Analysis (P31) (Average across runs)

Avg Time Taken

EXAONE-4.0.1-32B (high)
2301.7
Solar-Open-100B
640.8
K-EXAONE-236B-A23B
189.6
Gemini-3-Pro-Preview
170.7
Llama-VARCO-8B-Instruct
98.0
Deepseek-V3.2
67.5
HCX-007(high)
54.8
Solar-Pro-2 (31B)(high)
35.0
Kanana-2-30B-Thinking
33.8
Kanana-2-30B-Thinking-2601
21.2
A.X-4.0 (72B)
15.2
GPT-5.2 (high)
14.8
GPT-5.1 (high)
13.3
Claude-Opus-4.5
12.6
K-EXAONE-236B-A23B
12.4
Grok-4.1-fast
10.0

Avg Token Usage

EXAONE-4.0.1-32B (high)
37,496
K-EXAONE-236B-A23B
27,042
Kanana-2-30B-Thinking
7,460
Solar-Pro-2 (31B)(high)
7,096
HCX-007(high)
5,642
Kanana-2-30B-Thinking-2601
5,494
Solar-Open-100B
5,057
Llama-VARCO-8B-Instruct
4,580
GPT-5.2 (high)
4,360
Gemini-3-Pro-Preview
4,189
K-EXAONE-236B-A23B
4,115
Grok-4.1-fast
3,931
Deepseek-V3.2
3,561
Claude-Opus-4.5
3,451
A.X-4.0 (72B)
3,174
GPT-5.1 (high)
3,116