∣ ∣ ∣ x 2 + 4 x + 3 ∣ ∣ ∣ + 2 x + 5 = 0
The number of real solutions of the equation above is __________ .
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We have two cases: 1. When − x 2 − 4 x − 3 + 2 x + 5 = 0
− x 2 − 2 x + 2 = 0
x = − 1 ± 3
x 2 + 6 x + 8 = 0
x = − 2 , − 4
Sustitute in the original equation only − 2 and − 1 − 3 are solutions.
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We have, ∣ ∣ x 2 + 4 x + 3 ∣ ∣ + 2 x + 5
Here two cases arise.
⇒ x 2 + 4 x + 3 > 0
⇒ x 2 + 4 x + 3 + 2 x + 5 = 0
⇒ x 2 + 6 x + 8 = 0
⇒ Hence, x=-2, -4
Here, x=-2 doesn't satisfy x 2 + 4 x + 3 > 0 . So, x=-4 is the only solution for Case 1!
⇒ x 2 + 4 x + 3 < 0
⇒ − x 2 − 4 x − 3 + 2 x + 5 = 0
⇒ − x 2 − 2 x + 2 = 0
⇒ x 2 + 2 x − 2 = 0
⇒ x = − 1 + 3 , − 1 − 3
⇒ Hence, x = − ( 1 + 3 ) satisfies the given condition, while, x = − 1 + 3 doesn't!