Question

x²+x-7=5 ?

3x+2x²+5x=0 ?

3x²+7x+3=x²+2x ?

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Answer 1

x² + x - 7 = 5
x² + x - 7 - 5 = 0
x² + x - 12 = 0
Δ = b² - 4.a.c
Δ = 1² - 4 . 1 . -12
Δ = 1  + 48
Δ = 49 ⇒ √49 = 7
x = -b + ou - 7/2
x´= -1 + 7 / 2
x´= 6/2 = 3
x´´ = -1 - 7 / 2
x´´ = -8/2 = -4
S = {3;-4}

3 x + 2 x² + 5 x = 0
2 x² + 8 x = 0
2 x(x + 4) = 0
2 x = 0
x = 0/2 = 0
x + 4 = 0
x = - 4
S = {0 ; -4}

3 x² + 7 x + 3 = x² + 2 x
3 x² - x² + 7 x - 2 x + 3 = 0
2 x² + 5 x + 3 = 0
Δ = b² - 4.a.c
Δ = 5² - 4 .2.3
Δ = 25 - 24
Δ = 1  ⇒ √1 = 1
x = - b + ou - 1 / 2.2
x = -5 + 1 / 4
x´= -4/4 = -1
x´´ = -5 - 1 / 4
x´´ = -6/4 = -3/2
S = {-1 ; -3/2}