Problem Analysis #33

GPT-5.2 (high) · Run 1

154.84s
12,962 toks
Problem Statement

Let f(x)f(x) be a cubic function whose leading coefficient is positive, and let tt be a real number. Define

g(x)={f(x)(x<t),f(x)(xt),g(x) = \begin{cases}-f(x) & (x < t), \\[4pt]f(x) & (x \geq t),\end{cases}

so that gg is continuous on the entire real line and satisfies the following conditions.\begin{center}\fbox{\begin{minipage}{0.9\textwidth}(A) For every real number aa, the limit

limxa+g(x)x(x2)\displaystyle\lim_{x \to a^+} \dfrac{g(x)}{x(x-2)}

exists.KOR-CSAT-(B) The set of natural numbers mm for which

limxm+g(x)x(x2)\displaystyle\lim_{x \to m^+} \dfrac{g(x)}{x(x-2)}

is negative is

{g(1),72g(1)}.\left\{g(-1), -\dfrac{7}{2}g(1)\right\}.

\end{minipage}}\end{center}Assuming that g(1)eq72g(1)g(-1) eq -\dfrac{7}{2}g(1), compute g(5)g(-5). [4 points]\

Ground Truth
65
Execution Trace
Reasoning Process

[THOUGHT] Translate conditions into algebra. From (A), f(0)=f(2)=0, so f(x)=ax(x-2)*(x-r) with a>0. Continuity of g at t implies f(t)=0 so t is one of {0,2,r}. If t=r then g/(x(x-2)) becomes nonnegative a|x-r| so no negative limits, contradicting (B). If t=0 then for natural m we have g(1)=f(1)>0 making -(7/2)g(1)<0, impossible since it must be a natural number. Hence t=2. With t=2, for natural m the limit equals -a(m-r) for m<2 and a(m-r) for m>=2. To have exactly two negative m, r must be in (3,4], giving negative at m=2,3 only. Then {g(-1), -(7/2)g(1)} must equal {2,3}. Solve to find r and a, then compute g(-5). [/THOUGHT] [PYTHON] import sympy as sp

a, r = sp.symbols('a r', positive=True, real=True)

t = 2 case

g_minus1 = 3a(1+r) # derived g1 = a*(1-r) # since x=1<2 so g=-f, with f(1)=a(r-1) expr2 = -sp.Rational(7,2)*g1 # -(7/2)g(1) = (7/2)a(r-1)

Solve the only feasible assignment: g(-1)=3, expr2=2

sol = sp.solve([sp.Eq(g_minus1, 3), sp.Eq(expr2, 2)], [a, r], dict=True) print(sol)

sol = sol[0] a_val = sp.simplify(sol[a]) r_val = sp.simplify(sol[r]) print("a =", a_val, "r =", r_val)

Compute g(-5): for -5<2, g(-5) = -f(-5) = 35a(5+r)

g_minus5 = sp.simplify(35a_val(5+r_val)) print("g(-5) =", g_minus5)

Verify the set condition on natural m: compute sign for m=1..6

def L(m): m=sp.Rational(m,1) if m < 2: return sp.simplify(-a_val*(m-r_val)) else: return sp.simplify(a_val*(m-r_val)) for m in range(1,7): val=L(m) print(m, val, "negative?" , sp.sign(val)<0)

print("g(-1) =", sp.simplify(g_minus1.subs(sol))) print("-(7/2)g(1) =", sp.simplify(expr2.subs(sol))) [/PYTHON][THOUGHT] Translate conditions into algebra. From (A), f(0)=f(2)=0f(0)=f(2)=0, so f(x)=ax(x2)(xr)f(x)=a\,x(x-2)(x-r) with a>0a>0. Continuity at tt forces f(t)=0f(t)=0, hence t{0,2,r}t\in\{0,2,r\}.
If t=rt=r, then g(x)x(x2)\frac{g(x)}{x(x-2)} becomes nonnegative everywhere, contradicting (B).
If t=0t=0, then g(1)=f(1)>0g(1)=f(1)>0 so 72g(1)<0-\frac72 g(1)<0, impossible since it must be a natural number in (B). Thus t=2t=2.

With t=2t=2:
g(1)=3a(1+r)g(-1)=3a(1+r), g(1)=a(1r)g(1)=a(1-r), so 72g(1)=72a(r1)-\frac72 g(1)=\frac72 a(r-1).
The negative-limit naturals are {2,3}\{2,3\}, so {g(1),72g(1)}={3,2}\{g(-1),-\frac72 g(1)\}=\{3,2\}. Solving gives r=113r=\frac{11}{3}, a=314a=\frac{3}{14}.
Then for 5<2-5<2, g(5)=f(5)=35a(5+r)=65g(-5)=-f(-5)=35a(5+r)=65. 65\boxed{65}

Tool Output
[PYTHON OUTPUT] [{a: 3/14, r: 11/3}] a = 3/14 r = 11/3 g(-5) = 65 1 4/7 negative? False 2 -5/14 negative? True 3 -1/7 negative? True 4 1/14 negative? False 5 2/7 negative? False 6 1/2 negative? False g(-1) = 3 -(7/2)g(1) = 2 [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] The Python output gives g(5)=65g(-5)=65. Therefore the requested value is 65\boxed{65}.

Final Model Output
65

Comparative Analysis (P33) (Average across runs)

Avg Time Taken

Deepseek-V3.2
1184.1
K-EXAONE-236B-A23B
994.5
GPT-5.1 (high)
503.1
Solar-Open-100B
488.8
Solar-Pro-2 (31B)(high)
422.0
Grok-4.1-fast
366.9
K-EXAONE-236B-A23B
268.6
Kanana-2-30B-Thinking
188.6
Gemini-3-Pro-Preview
183.0
Kanana-2-30B-Thinking-2601
170.5
GPT-5.2 (high)
154.8
EXAONE-4.0.1-32B (high)
152.2
Llama-VARCO-8B-Instruct
151.6
Claude-Opus-4.5
47.4
A.X-4.0 (72B)
27.8
HCX-007(high)
22.6

Avg Token Usage

K-EXAONE-236B-A23B
100,286
Solar-Open-100B
70,810
K-EXAONE-236B-A23B
58,118
Grok-4.1-fast
57,340
Kanana-2-30B-Thinking-2601
34,034
Kanana-2-30B-Thinking
29,518
GPT-5.1 (high)
29,140
Deepseek-V3.2
25,475
Solar-Pro-2 (31B)(high)
20,065
Gemini-3-Pro-Preview
17,873
GPT-5.2 (high)
12,962
Llama-VARCO-8B-Instruct
9,839
Claude-Opus-4.5
8,374
EXAONE-4.0.1-32B (high)
5,810
A.X-4.0 (72B)
2,546
HCX-007(high)
2,466