Question

Решить уравнения:

1. 2х2-18=0
2. 3х2-12х=0
3. 2,7х2=0
4. х2+16=0
5. х2- =0
6. х2=7х
7. х2-3х-5=11-3х
8. х2=2,5
помогите пжж

1. 2х2-18=0
2. 3х2-12х=0
3. 2,7х2=0
4. х2+16=0
5. х2- =0
6. х2=7х
7. х2-3х-5=11-3

Answer 1

Объяснение:

N°1:

$2 {x}^{2} - 18 = 0 | \div 2 \\ {x}^{2} - 9 = 0 \\ (x - 3)(x + 3) = 0 \\ x = \pm 3$

N°2:

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

N°3:

$2.7 {x}^{2} = 0 | \div 2.7 \\ {x}^{2} = 0 \\ x = 0$

N°4:

${x}^{2} + 16 = 0 \\ {x}^{2} = - 16 \\ x \: \in \: \varnothing$

N°5:

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

N°6:

${x}^{2} = 7x \\ {x}^{2} - 7x = 0 \\ x(x - 7) = 0 \\ x = 0 \: \: \: x = 7$

N°7:

${x}^{2} - 3x - 5 = 11 - 3x \\ {x}^{2} - 3x - 5 - 11 + 3x = 0 \\ {x}^{2} - 16 = 0\\ (x - 4)(x + 4) = 0 \\ x = \pm 4$

N°8:

${x}^{2} = 2.5 \\ {x}^{2} - 2.5 = 0 \\ {x}^{2} - \frac{10}{4} = 0 \\ (x - \sqrt{ \frac{10}{4} } )(x + \sqrt{ \frac{10}{4} } ) = 0 \\ (x - \frac{ \sqrt{10} }{2} )(x + \frac{ \sqrt{10} }{2} ) = 0 \\ x = \pm \frac{ \sqrt{10} }{2}$