## Giải dùm mik. Mik sắp ik học r Nhanh lên ạ

Question

Giải dùm mik. Mik sắp ik học r
Nhanh lên ạ

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9 months 2020-10-29T15:52:57+00:00 1 Answers 73 views 0

$$\begin{array}{l} P = {\left( {a + 1} \right)^2} + {\left( {b + 1} \right)^2} + {\left( {c + 1} \right)^2} + 2.\left( {ab + ac + bc} \right)\\ = \left( {{a^2} + 2a + 1} \right) + \left( {{b^2} + 2b + 1} \right) + \left( {{c^2} + 2c + 1} \right) + 2.\left( {ab + ac + bc} \right)\\ = \left( {{a^2} + {b^2} + {c^2}} \right) + 2.\left( {ab + bc + ca} \right) + 2.\left( {a + b + c} \right) + 1\\ Q = {\left( {a + b + c + 1} \right)^2}\\ = {\left[ {\left( {a + b} \right) + \left( {c + 1} \right)} \right]^2}\\ = {\left( {a + b} \right)^2} + 2.\left( {a + b} \right).\left( {c + 1} \right) + {\left( {c + 1} \right)^2}\\ = \left( {{a^2} + 2ab + {b^2}} \right) + 2\left( {ac + a + bc + b} \right) + \left( {{c^2} + 2c + 1} \right)\\ = \left( {{a^2} + {b^2} + {c^2}} \right) + 2.\left( {ab + bc + ca} \right) + 2.\left( {a + b + c} \right) + 1\\ \Rightarrow P – Q = 2 \end{array}$$