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Find all roots. Answer as soon as possible. Explain how to do it.

Find all roots. Answer as soon as possible. Explain how to do it.-example-1
User Swapneel
by
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2 Answers

5 votes

Answer:

x = ± 3

Explanation:


x {}^(4) - 5x {}^(2) - 36 = 0 \\ let \: x {}^(2) = y \: (subtitution) \\ (x {}^(2) ) {}^(2) - 5x {}^(2) - 36 = 0 \\ y {}^(2) - 5y - 36 = 0 \\ (y + 4)(y - 9) = 0 \\ y = - 4 \: \: \: \: \: \: \: \: \: \ \: y = 9 \\ (y = x {}^(2) ) \\ x {}^(2) = - 4 \: \: \: \: \: \: \: \: \: \: \: \: \: x {}^(2) = 9

We can't take the square root of a negative number so x² = -4 is rejected


x {}^(2) = 9 \\ x = √(9) = \binom{ + }{ - } 3

Therefore

x = 3

x = -3

User Nickeshia
by
8.6k points
3 votes

Answer:

2i, -2i, -3, 3

Explanation:

We can complete the square to factor but make x to the power of 2 since the variable x is squared in the function aswell

Factor

(
x^(2) + 4)(
x^(2) - 9)

Now we have two function we can set equal to 0

Find zeros


x^(2) + 4 = 0


x^(2) - 9 = 0


x^(2) = 9


x^(2) = -4

x =
√(-4)

x =
√(9)

±2i, ±3

User Denisa
by
8.4k points

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