Bonjour
1) f(x) = (x + 6)² - 25 = (x + 6)² - 5² = (x + 6 - 5)(x + 6 + 5)
f(x) = (x + 1)(x + 11)
x + 1 ≥ 0 ------> x ≥ -1 ; x + 11 ≥ 0 -----> x ≥ -11
donc f(x) ≥ 0 sur ]-oo ; -11] U [-1 ; +oo[
f(x) ≤ 0 sur [-11 ; -1]
2) g(x) = (5x - 3)² - (x - 4)² = (5x - 3 - (x-4))(5x - 3 + x - 4)
g(x) = (4x + 1)(6x - 7)
4x + 1 ≥ 0 ------> x
