The product of four numbers is 540. Three of the four numbers are 2, 5 and 9. What is the other number?
2 answers:
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Answer:
{ - 2, 10 }
Step-by-step explanation:
Given
x² - 8x = 20
To complete the square
add ( half the coefficient of the x- term )² to both sides
x² + 2(- 4)x + 16 = 20 + 16, that is
(x - 4)² = 36 ( take the square root of both sides )
x - 4 = ± = ± 6 ( add 4 to both sides )
x = 4 ± 6
Thus
x = 4 - 6 = - 2
x = 4 + 6 = 10