F(x)=ax²+2√2x+(a-1) D>0

f(x)=ax²+2√2x+(a-1)

D>0 ⇒ b² – 4ac > 0

(2√2)² – 4(a)(a-1) > 0

8 – 4a² + 4a > 0   x-1/4

a² – a – 2 < 0

(a – 2)(a + 1) < 0

-1 < a < 2