Réponse :
x ∈]2 ; + ∞[
1) montrer que (x² - x - 3)/(x - 2) = x + 1 - (1/(x - 2)
(x² - x - 3)/(x - 2) = (x² - x - 2 - 1)/(x - 2)
= (x² - x - 2)/(x - 2) - (1/(x - 2)
x² - x - 2 = x² - x - 2 + 1/4 - 1/4
= x² - x + 1/4 - 9/4
= (x - 1/2)² - 9/4 = (x - 1/2 + 3/2)(x - 1/2 - 3/2) = (x + 1)(x - 2)
(x² - x - 2)/(x - 2) - (1/(x - 2) = (x + 1)(x - 2)/(x - 2) - 1/(x - 2)
= x + 1 - (1/(x - 2)
2) montrer que (2 x² + x - 10)/(x² - 4) = (2 x + 5)/(x + 2)
2 x² + x - 10 = 2(x² + 1/2) x - 5)
= 2(x² + (1/2) x - 5 + 1/16 - 1/16)
= 2(x² + (1/2) x + 1/16 - 81/16)
= 2((x + 1/4)² - 81/16)
= 2((x + 1/4 + 9/4)(x + 1/4 - 9/4)
= 2(x + 5/2)(x - 2)
= (2 x + 5)(x - 2)
(2 x² + x - 10)/(x² - 4) = (2 x + 5)(x - 2)/(x - 2)(x + 2)
= (2 x + 5)/(x + 2)
Explications étape par étape
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Réponse :
x ∈]2 ; + ∞[
1) montrer que (x² - x - 3)/(x - 2) = x + 1 - (1/(x - 2)
(x² - x - 3)/(x - 2) = (x² - x - 2 - 1)/(x - 2)
= (x² - x - 2)/(x - 2) - (1/(x - 2)
x² - x - 2 = x² - x - 2 + 1/4 - 1/4
= x² - x + 1/4 - 9/4
= (x - 1/2)² - 9/4 = (x - 1/2 + 3/2)(x - 1/2 - 3/2) = (x + 1)(x - 2)
(x² - x - 2)/(x - 2) - (1/(x - 2) = (x + 1)(x - 2)/(x - 2) - 1/(x - 2)
= x + 1 - (1/(x - 2)
2) montrer que (2 x² + x - 10)/(x² - 4) = (2 x + 5)/(x + 2)
2 x² + x - 10 = 2(x² + 1/2) x - 5)
= 2(x² + (1/2) x - 5 + 1/16 - 1/16)
= 2(x² + (1/2) x + 1/16 - 81/16)
= 2((x + 1/4)² - 81/16)
= 2((x + 1/4 + 9/4)(x + 1/4 - 9/4)
= 2(x + 5/2)(x - 2)
= (2 x + 5)(x - 2)
(2 x² + x - 10)/(x² - 4) = (2 x + 5)(x - 2)/(x - 2)(x + 2)
= (2 x + 5)/(x + 2)
Explications étape par étape