[tex]1. \: {(2c + b)}^{2} = {4c}^{2} + 4cb + {b}^{2} \\ 2. \: {(c + b)}^{2} - 2cb = {c}^{2} + 2cb + {b}^{2} - 2cb = {c}^{2} + {b}^{2} \\ 3. \: {b}^{2} - 9 {c}^{2} = (b - 3c)(b + 3c) \\ 4. \: {(b + 3c)}^{2} - 3c(3c + 2b) = {b}^{2} + 6cb + {9c}^{2} - {9c}^{2} - 6cb = {b}^{2} [/tex]
Ответ : 1 - В); 2 - А); 3 - Д); 4 - Б)
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[tex]1. \: {(2c + b)}^{2} = {4c}^{2} + 4cb + {b}^{2} \\ 2. \: {(c + b)}^{2} - 2cb = {c}^{2} + 2cb + {b}^{2} - 2cb = {c}^{2} + {b}^{2} \\ 3. \: {b}^{2} - 9 {c}^{2} = (b - 3c)(b + 3c) \\ 4. \: {(b + 3c)}^{2} - 3c(3c + 2b) = {b}^{2} + 6cb + {9c}^{2} - {9c}^{2} - 6cb = {b}^{2} [/tex]
Ответ : 1 - В); 2 - А); 3 - Д); 4 - Б)