Explications étape par étape:

1) f(3) = (4×3²) - 7 = 36 - 7 = 29

2) f(-5) = (4 × (-5)²) - 7 = 100 - 7 = 93

3) 4x² - 7 = -3

4x² = = -3 + 7 = 4

x² = 4/4 = 1 ou -1