Question

(х-1)(х-7)(х-4)(х+2)=40 епрноеен

Answer 1

(х-1)(х-7)(х-4)(х+2)=40

(х-1)(х-4)(х-7)(х+2)=40

(x² -4x -x + 4)(x² + 2x - 7x - 14) = 40

(x² -5x + 4)(x² - 5x - 14) = 40

x² - 5x - 5 = t замена

(t + 9)(t - 9) = 40

t² - 81 = 40

t² = 121

t = +- 11

обратно

1. t = 11

x² - 5x - 5 = 11

x² - 5x - 16 = 0

D = b² - 4ac = 25 + 64 = 89

x12 = (5 +- √89)/2

2. x = -11

x² - 5x - 5 = -11

x² - 5x + 6 = 0

D = b² - 4ac = 25 - 24 = 1

x34 = (5 +- 1)/2 = 3   2

ответ x = {2,3,(5 + √89)/2,(5 - √89)/2}

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