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Bunuel
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Hello Chethan92!

I did it the same way as you but I have a question.

When you try C and D, both are greater than 0.

How did you choose D?

\(a^2 - 4b > 0\)

C \((1 ,-2)\)

\(1^2 - 4(-2) > 0\)

\(9 > 0\) True


D \((2 ,-1)\)

\(2^2 - 4(-1) > 0\)

\(8 > 0\) True
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jfranciscocuencag
Hello Chethan92!

I did it the same way as you but I have a question.

When you try C and D, both are greater than 0.

How did you choose D?

\(a^2 - 4b > 0\)

C \((1 ,-2)\)

\(1^2 - 4(-2) > 0\)

\(9 > 0\) True


D \((2 ,-1)\)

\(2^2 - 4(-1) > 0\)

\(8 > 0\) True

Hey jfranciscocuencag, How are you?

Yes, even I noticed it. But I missed it while I was answering this question. Maybe D option should be some other value as the answer is C.
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Bunuel
Suppose that a and b are nonzero real numbers, and that the equation x^2 + ax + b = 0 has solutions a and b. Then the pair (a,b) is

(A) (-2, 1)
(B) (-1, 2)
(C) (1, -2)
(D) (2, -1)
(E) (4, 4)

We can create the equation:


Since we are given that the roots are a and b, we can write:

(x - a)(x - b) = 0

x^2 - ax - bx + ab = 0

x^2 - (a + b)x + ab = 0

Now, we compare the equation obtained above to the original equation x^2 + ax + b = 0, obtaining:

a = -(a + b) and b = ab. Since neither a nor b is 0, then a must be 1 so that b = ab, and we have:

1 = -(1 + b)

1 = -1 - b

b = -2

Answer: C
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Bunuel
Suppose that a and b are nonzero real numbers, and that the equation x^2 + ax + b = 0 has solutions a and b. Then the pair (a,b) is

(A) (-2, 1)
(B) (-1, 2)
(C) (1, -2)
(D) (2, -1)
(E) (4, 4)

\((x-a)(x-b)=0…x^2-xb-ax+ab=0…x^2-(a+b)x+ab=0\)
\(x^2 + [a]x + [b] = 0…[b]=ab…a=1…[a]=-(a+b)…1=-1-b…b=-2\)
\((a,b)=(1,-2)\)

Answer (C)
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