bonsoir
f (x) = 5 - x²
f ( - 3 ) = 5 - ( 9 ) = 5 - 9 = - 4
f ( 3 /4 ) = 5 - ( 3/4 )² = 5 - 9/16 = 80/16 - 9 /16 = 64/16 = 4
f ( √3) = 5 - ( √3)² = 5 - 3 = 2
5 - x² = - 20
- x² = - 20 - 5
- x² = - 25
x ² = 25
x = √25 ou - √5
x = 5 ou - 5
5 - x² = 6
- x² = 6 - 5
- x² = 1
x ² = - 1 ⇔ pas de solution dans R
f (x) = 4 x² + 20 x + 25
f (x) = ( 2 x + 5 )²
f (x) = 0 ⇔ x = - 5/2
le reste , tu lis sur la courbe
