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Anyone know the answer to this?

Anyone know the answer to this?-example-1
User Ahay
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1 Answer

4 votes

Answer:

x^4 - 7x^3 +7x^2 +21x-30

Explanation:

If the roots of the function are 2 sqrt(3) and 5

We know that there is one more root

Irrational roots come in pairs, if we have a +sqrt (b), we have a - sqrt(b)

Since we have 0+sqrt(3) we will also have 0-sqrt(3)

We can write the polynomial using the roots

2, sqrt(3) (-sqrt(3) 5 are our roots

0= (x-a) (x-b) (x-c) (x-d) where a,b,c,d are the 4 roots

0 = (x-2) (x-5) (x-sqrt(3)) (x--sqrt(3))

0 = (x-2) (x-5) (x-sqrt(3)) (x+sqrt(3))

FOIL the first two terms

(x-2) (x-5) = x^2 -5x-2x+10 = x^2 -7x+ 10

FOIl the last two terms

(x-sqrt(3)) (x+sqrt(3)) = x^2 - xsqrt(3) + xsqrt(3) - 3 = x^2 -3

0 = (x-2) (x-5) (x-sqrt(3)) (x+sqrt(3))

0 = (x^2 -7x+10) (x^2 -3)

Multiply x^2 by everything in the first term

x^2 (x^2 -7x+10) =x^4 - 7x^3 + 10x^2

Multiply -3 by everything in the first term

-3 (x^2 -7x+ 10) = -3x^2 +21x -30

Add these results together

x^4 - 7x^3 + 10x^2

-3x^2 +21x -30

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x^4 - 7x^3 +7x^2 +21x-30

User Mcku
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