যদি a+b+c=9,ab+bc+ca=31 হয়, তবে a2+b2+c2= কত ?

যদি a+b+c=9,ab+bc+ca=31 হয়, তবে a2+b2+c2= কত ? Correct Answer 19

দেয়া আছে,<math xmlns = "http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo> + </mo><mi>b</mi><mo> + </mo><mi>c</mi><mo> = </mo><mn>9</mn><mspace linebreak = "newline"/><mi>a</mi><mi>b</mi><mo> + </mo><mi>b</mi><mi>c</mi><mo> + </mo><mi>c</mi><mi>a</mi><mo> = </mo><mn>31</mn><mspace linebreak = "newline"/><mo>&#x2234;</mo><msup><mi>a</mi><mn>2</mn></msup><mo> + </mo><msup><mi>b</mi><mn>2</mn></msup><mo> + </mo><msup><mi>c</mi><mn>2</mn></msup><mo> = </mo><msup><mfenced><mrow><mi>a</mi><mo> + </mo><mi>b</mi><mo> + </mo><mi>c</mi></mrow></mfenced><mn>2</mn></msup><mo> - </mo><mn>2</mn><mfenced><mrow><mi>a</mi><mi>b</mi><mo> + </mo><mi>b</mi><mi>c</mi><mo> + </mo><mi>c</mi><mi>a</mi></mrow></mfenced><mspace linebreak = "newline"/><mo> = </mo><msup><mn>9</mn><mn>2</mn></msup><mo> - </mo><mn>2</mn><mo>&#xD7;</mo><mn>31</mn><mspace linebreak = "newline"/><mo> = </mo><mn>81</mn><mo> - </mo><mn>62</mn><mspace linebreak = "newline"/><mo> = </mo><mn>19</mn></math>