bonsoir
g (x) = 2 x² - 1
il sufit de remplacer x
f ( 3) = 2 *3² - 1 = 18 - 1 = 17
f ( - 2 ) = 2 ( - 2 )² - 1 = 8 - 1 = 7
2 x² - 1 = 1
2 x² = 1 + 1
2 x² = 2
x² = 1
x = √1 ou - √ 1
2 x² - 1 = - 1
2 x² = - 1 + 1
2 x² = 0
x = 0
2 x² - 1 = - 3
2 x² = - 3 + 1
2 x² = - 2
x² = - 1
pas de solution
