Verified answer

Формулы:

D = b^2 - 4ac

x1 = - b - √D / 2a

x2 = - b + √D / 2a

№26.

x^2+ 3x + 2 = 0

a = 1

b = 3

c = 2

D = 3^2 - 4 × 1× 2 = 9 - 8 = 1 D > 0

x1 = - 3 - √1 / 2 × 1 = - 3 - 1 / 2 = - 4

x2 = - 3 + 1 / 2 = - 2 / 2 = - 1

Ответ: - 2 ; -1.

№27.

x^2 + 4x + 3 = 0

a = 1

b = 4

c = 3

D = 4^2 - 4 × 1 × 3 = 16 - 12 = 4 D > 0

x1 = - 4 - √4 / 2 × 1 = - 4 - 2 / 2 = -6 / 2 = - 3

x2 = - 4 + 2 / 2 = -2 / 2 = - 1

Ответ: - 3 ; - 1.

№28.

x^2 + 5x + 4 = 0

a = 1

b = 5

c = 4

D = 5^2 - 4 × 1 × 4 = 25 - 16 = 9 D > 0

x1 = - 5 - √9 / 2 = - 5 - 3 / 2 = - 8 / 2 = - 4

x2 = - 5 + 3 / 2 = - 2 / 2 = - 1

Ответ: - 4 ; - 1.

№29.

x^2 + 6x + 5 = 0

a = 1

b = 6

c = 5

D = 6^2 - 4 × 1 × 5 = 36 - 20 = 16 D > 0

x1 = - 6 - 4 / 2 = - 10 / 2 = - 5

x2 = - 6 + 4 / 2 = - 2 / 2 = - 1

Ответ: - 5 ; - 1.

№30.

x^2 + 10x + 9 = 0

a = 1

b = 10

c = 9

D = 10^2 - 4 × 1 × 9 = 100 - 36 = 64 D > 0

x1 = - 10 - 8 / 2 = - 18 / 2 = - 9

x2 = - 10 + 8 / 2 = - 2 / 2 = - 1

Ответ: - 9 ; - 1.

№31.

x^2 + 16x + 15 = 0

a = 1

b = 16

c = 15

D = 16^2 - 4 × 1 × 15 = 256 - 60 = 196

x1 = - 16 - √196 / 2 = - 16 - 14 / 2 = - 30 / 2 = - 15

x2 = - 16 + 14 / 2 = - 2 / 2 = - 1

Ответ: - 15 ; - 1.

№32.

x^2 + 8x + 15 = 0

a = 1

b = 8

c = 15

D = 8^2 - 4 × 1 × 15 = 64 - 60 = 4

x1 = - 8 - 2 / 2 = - 10 / 2 = - 5

x2 = - 8 + 2 / 2 = - 6 / 2 = - 3

Ответ: - 5 ; - 3.

№33.

x^2 + 17x + 16 = 0

a = 1

b = 17

c = 16

D = 17^2 - 4 × 1 × 16 = 289 - 64 = 225

x1 = - 17 - √225 / 2 = - 17 - 15 / 2 = - 32 / 2 = - 16

x2 = - 17 + 15 / 2 = - 2 / 2 = - 1

Ответ: - 16 ; - 1

№34.

x^2 + 10x + 16 = 0

a = 1

b = 10

c = 16

D = 100 - 64 = 36

x1 = - 10 - 6 / 2 = - 16 / 2 = - 8

x2 = - 10 + 6 / 2 = - 4 / 2 = - 2

Ответ: - 8 ; - 2.

№35.

x^2+ 19x + 18 = 0

a = 1

b = 19

c = 18

D = 361 - 72 = 289

x1 = - 19 - 17 / 2 = - 36 / 2 = - 18

x2 = - 19 + 17 / 2 = - 2 / 2 = -1

Ответ: - 18 ; - 1.

№36.

x^2 + 11x + 18 = 0

a = 1

b = 11

c = 18

D = 11^2 - 4 × 18 = 121 - 72 = 49

x1 = - 11 - 7 / 2 = - 18 / 2 = - 9

x2 = - 4 / 2 = - 2

Ответ: - 9 ; - 2.

№37.

x^2 + 9x + 18 = 0

a = 1

b = 9

c = 18

D = 81 - 72 = 9

x1 = - 9 - 3 / 2 = - 12 / 2 = - 6

x2 = - 6 / 2 = - 3

Ответ: - 6 ; - 3.

№38.

x^2 + 21x + 20 = 0

a = 1

b = 21

c = 20

D = 441 - 80 = 361

x1 = - 21 - 19 / 2 = - 40 / 2 = - 20

x2 = - 21 + 19 / 2 = - 1

Ответ: - 20 ; - 1.

№39.

x^2 + 12x + 20 = 0

a = 1

b = 12

c = 20

D = 144 - 80 = 64

x1 = - 12 - 8 / 2 = - 20 / 2 = - 10

x2 = - 4 / 2 = - 2

Ответ: - 10 ; - 2.

№40.

x^2 + 9x + 20 = 0

a = 1

b = 9

c = 20

D = 81 - 80 = 1

x1 = - 9 - 1 / 2 = - 10 / 2 = - 5

x2 = - 8 / 2 = - 4

Ответ: - 5 ; - 4.