OG 12th edition - Q # 173

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OG 12th edition - Q # 173

by bhumika.k.shah » Fri Feb 05, 2010 6:58 am
173. Which of the following describes all values of x for
which 1 - x2 ≥ 0 ?
(A) x ≥ 1
(B) x ≤ -1
(C) 0 ≤ x ≤ 1
(D) x ≤ -1 or x ≥ 1
(E) -1 ≤ x ≤ 1

I got (1-x) ( 1+x) ≥ 0
what next ?
dint quite understand the explanation in OG
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by ajith » Fri Feb 05, 2010 7:17 am
bhumika.k.shah wrote:173. Which of the following describes all values of x for
which 1 - x2 ≥ 0 ?
(A) x ≥ 1
(B) x ≤ -1
(C) 0 ≤ x ≤ 1
(D) x ≤ -1 or x ≥ 1
(E) -1 ≤ x ≤ 1

I got (1-x) ( 1+x) ≥ 0
what next ?
dint quite understand the explanation in OG
(1-x) ( 1+x) ≥ 0

now this can happen when

1. 1-x ≥ 0 and 1+x ≥ 0

x≤1 and x ≥ -1
or -1 ≤ x ≤ 1

2. 1-x ≤ 0 and 1+x ≤ 0
x≥1 and x≤ -1
Which is not possible

so; E
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