We are tasked with finding how many prime numbers <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math>p make the expression <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>3</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mi>p</mi><mo>+</mo><mn>1</mn><mo>+</mo><mn>7</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mi>p</mi><mo>+</mo><mn>1</mn></mrow><annotation encoding="application/x-tex">3p^2 + p + 1 + 7p^2 + p + 1</annotation></semantics></math>3p2+p+1+7p2+p+1 divisible by <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math>p.
First, simplify the given expression:
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>3</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mi>p</mi><mo>+</mo><mn>1</mn><mo>+</mo><mn>7</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mi>p</mi><mo>+</mo><mn>1</mn><mo>=</mo><mo stretchy="false">(</mo><mn>3</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mn>7</mn><msup><mi>p</mi><mn>2</mn></msup><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mi>p</mi><mo>+</mo><mi>p</mi><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mn>1</mn><mo>+</mo><mn>1</mn><mo stretchy="false">)</mo><mo>=</mo><mn>10</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mn>2</mn><mi>p</mi><mo>+</mo><mn>2.</mn></mrow><annotation encoding="application/x-tex">3p^2 + p + 1 + 7p^2 + p + 1 = (3p^2 + 7p^2) + (p + p) + (1 + 1) = 10p^2 + 2p + 2.</annotation></semantics></math>3p2+p+1+7p2+p+1=(3p2+7p2)+(p+p)+(1+1)=10p2+2p+2.Now, we want to determine for which prime numbers <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math>p, the expression <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>10</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mn>2</mn><mi>p</mi><mo>+</mo><mn>2</mn></mrow><annotation encoding="application/x-tex">10p^2 + 2p + 2</annotation></semantics></math>10p2+2p+2 is divisible by <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math>p. To do this, we need to check the divisibility condition:
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>10</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mn>2</mn><mi>p</mi><mo>+</mo><mn>2</mn><mo>≡</mo><mn>0</mn><mspace></mspace><mspace width="1em"></mspace><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">d</mi></mrow><mspace width="0.3333em"></mspace><mi>p</mi><mo stretchy="false">)</mo><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">10p^2 + 2p + 2 \equiv 0 \pmod{p}.</annotation></semantics></math>10p2+2p+2≡0(modp).By reducing the expression modulo <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math>p, we get:
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>10</mn><msup><mi>p</mi><mn>2</mn></msup><mo>+</mo><mn>2</mn><mi>p</mi><mo>+</mo><mn>2</mn><mo>≡</mo><mn>0</mn><mspace></mspace><mspace width="1em"></mspace><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">d</mi></mrow><mspace width="0.3333em"></mspace><mi>p</mi><mo stretchy="false">)</mo><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">10p^2 + 2p + 2 \equiv 0 \pmod{p}.</annotation></semantics></math>10p2+2p+2≡0(modp).Since <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mi>p</mi><mn>2</mn></msup><mo>≡</mo><mn>0</mn><mspace></mspace><mspace width="0.4444em"></mspace><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">d</mi></mrow><mspace width="0.3333em"></mspace><mi>p</mi><mo stretchy="false">)</mo></mrow><annotation encoding="application/x-tex">p^2 \equiv 0 \pmod{p}</annotation></semantics></math>p2≡0(modp) and <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mo>≡</mo><mn>0</mn><mspace></mspace><mspace width="0.4444em"></mspace><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">d</mi></mrow><mspace width="0.3333em"></mspace><mi>p</mi><mo stretchy="false">)</mo></mrow><annotation encoding="application/x-tex">p \equiv 0 \pmod{p}</annotation></semantics></math>p≡0(modp), the expression simplifies to:
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>10</mn><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>+</mo><mn>2</mn><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>+</mo><mn>2</mn><mo>≡</mo><mn>2</mn><mspace></mspace><mspace width="1em"></mspace><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">d</mi></mrow><mspace width="0.3333em"></mspace><mi>p</mi><mo stretchy="false">)</mo><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">10(0) + 2(0) + 2 \equiv 2 \pmod{p}.</annotation></semantics></math>10(0)+2(0)+2≡2(modp).Therefore, the condition becomes:
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>2</mn><mo>≡</mo><mn>0</mn><mspace></mspace><mspace width="1em"></mspace><mo stretchy="false">(</mo><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">d</mi></mrow><mspace width="0.3333em"></mspace><mi>p</mi><mo stretchy="false">)</mo><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">2 \equiv 0 \pmod{p}.</annotation></semantics></math>2≡0(modp).This implies that <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math>p must divide 2. The only prime number that divides 2 is <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mo>=</mo><mn>2</mn></mrow><annotation encoding="application/x-tex">p = 2</annotation></semantics></math>p=2.
Thus, the only prime number that satisfies the divisibility condition is <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mo>=</mo><mn>2</mn></mrow><annotation encoding="application/x-tex">p = 2</annotation></semantics></math>p=2.
Answer: There is 1 prime number, which is <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mo>=</mo><mn>2</mn></mrow><annotation encoding="application/x-tex">p = 2</annotation></semantics></math>p=2.
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