✘² = -1
S = { i }
Car i² = -1
b)
49✘² = -14✘ -1
49✘² + 14✘ + 1 = 0
∆ = b² -4ac
∆= 14² - 4×49×1
∆ = 0
L’équation ne possède qu’une solution :
✘₀ = -b/2a
= -14/2×49
= -1/7
S = { -1/7}
c)
(2✘-6)² -(✘+3)² = 0
4✘ -48✘+36 -✘² + 6✘ + 9 = 0
-✘² - 42✘ + 45 = 0
∆ = b² -4ac
∆ = (-42)² - 4×(-1)×45
∆ = 576
L’équation a 2 solutions
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