nonzero roots

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nonzero roots

by sanju09 » Tue Mar 03, 2009 5:03 am
If a and b are the nonzero roots of the quadratic equation x^2 + a x + b = 0, then
A. a = 1 and b = −4
B. a = 1 and b = −2
C. a = −1 and b = −4
D. a = −1 and b = 2
E. a = −1 and b = 4
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by bluementor » Tue Mar 03, 2009 5:44 am
x^2 + a x + b = 0 (Eqn 1)

a and b are the nonzero roots:
(x-a)(x-b)=0
x^2 -ax -bx + ab = 0
x^2 -(a+b)x + ab = 0 (Eqn 2)

Comparing equations 1 and 2:

Product of both roots = b
ab = b
a=1

Sum of both roots = -a
a + b = -a
2a = -b
b = -2

Choose B

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