Помогите срочно 20 балов. Created by Sadigg. algebra-ru

Ответ:1. Б2. А3. В4. Б5. В6. ГКорней нет7. Б8. В9.

Помогите срочно 20 балов...

elenamuraweva

Ответ:

1. Б

2. А

3. В

${x}^{2} - 49 = 0 \\ (x - 7)(x + 7) = 0 \\ 1)x - 7 = 0 \\ x = 7 \\ 2)x + 7 = 0 \\ x = - 7$

4. Б

$4 {x}^{2} = 0 \\ {x}^{2} = 0 \div 4 \\ {x}^{2} = 0 \\ x = 0$

5. В

${x}^{2} - 16x = 0 \\ x(x - 16) = 0 \\ 1)x = 0 \\ 2)x - 16 = 0 \\ x = 16$

6. Г

$- 3 {x}^{2} - 12 = 0 \\ - 3 {x}^{2} = 12 \\ {x}^{2} = 12 \div ( - 3) \\ {x}^{2} = - 4$

Корней нет

7. Б

$2 {x}^{2} + 16x = 0 \\ 2x(x + 8) = 0 \\ 1)2x = 0 \\ x = 0 \div 2 \\ x = 0 \\ 2)x + 8 = 0 \\ x = - 8$

$0 \times ( - 8) = 0$

8. В

$2 {x}^{2} - 50 = 0 \\ 2 {x}^{2} = 50 \\ {x}^{2} = 50 \div 2 \\ {x}^{2} = 25 \\ {x}^{2} - 25 = 0 \\ (x - 5)(x + 5) = 0 \\ 1)x - 5 = 0 \\ x = 5 \\ 2)x + 5= 0 \\ x = - 5$

$5 - 3x - 2 {x}^{2} = - 5 {x}^{2} - 3x + 29 \\ - 2 {x}^{2} + 5 {x}^{2} - 3x + 3x + 5 - 29 = 0 \\ 3 {x}^{2} - 24 = 0 \\ 3 {x}^{2} = 24 \\ {x}^{2} = 24 \div 3 \\ {x}^{2} = 8 \\ {x}^{2} - 8 = 0 \\ (x - \sqrt{8} )(x + \sqrt{8} ) = 0 \\ 1)x - \sqrt{8} = 0 \\ x = \sqrt{8} \\x = \sqrt{4 \times 2} \\ x = \sqrt{4} \times \sqrt{2} \\ x = 2 \sqrt{2} \\ 2)x + \sqrt{8} = 0 \\ x = - \sqrt{8} \\ x = - 2 \sqrt{2}$

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