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PilotLPTM [1.2K]
3 years ago
5

X² - 4x +40=0 How do I solve this

Mathematics
1 answer:
sineoko [7]3 years ago
8 0

Answer:

x = 2 + 6i, x - 6i.

Step-by-step explanation:

To factor this you need 2 numbers whose product is + 40 and whose sum is -4. There are no such numbers so we could use the method of completing the square:

x^2 - 4x + 40 = 90

x^2 - 4x = -40

(x - 2)^2 - 4 = -40

(x - 2)^2 = -36     -  So the roots are complex numbers:

x - 2 = +/-√36

x = 2 + 6i, x - 6i.

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1. Remove unnecessary parentheses

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2. Combine like terms (ex: r and -2r, n and 4n)

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Therefore, the correct answer is B.

Hope this helps!

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