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Ответ

Ответ дан
sophiaesliche

Ответ:

x1=2,125; x2=2,5

Объяснение:

4(10x−21)^2-(10x-21)-16(10x-21)+4=0,

(10x-21)×(4(10x-21)-1)-4(4(10x-21)-1)=0,

(4(10x-21)-1)×(10x-21-4)=0,

(40x-84-1)×(10x-25)=0,

(40x-85)×5(2x-5)=0,

5(8x-17)×5(2x-5)=0 делим обе части уравнения на 5,

(8x-17)×(2x-5)=0.

Произведение равно нулю, когда хотя бы один из множителей равен нулю. Следовательно:

8x-17=0 или 2x-5=0

x=17/8 или x=5/2

x=2,125 или x=2,5

Ответ

Проверено экспертом

Ответ дан
mmb1

4(10x−21)^2−17(10x−21)+4=0

10х - 21 = t

4t² - 17t + 4 = 0

D = 17² - 4*4*4 = 289 - 62 = 225

t12 = (17 +- 15)/8 = 4    1/4

1. t1 = 4

10x - 21 = 4

10x = 25

x = 25/10 = 5/2 = 2.5

2. t2 = 1/4

10x - 21 = 1/4

40x - 84 = 1

40x = 85

x = 85/40 = 17/8 = 2.125

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