bsr

UN exercice => CET exercice

x² + 3x = 28

x² + 3x - 28 = 0

Δ = 3² - 4*(-)28 = 9 + 112 = 121 = 11²

x' = (-3-11)/2 = -7

x'' = (-3+11) / 2 = 4

=> S = {-7 ; 4}

2x² + 7x + 3 + 2 = 0

2x² + 7x + 5 = 0

Δ = 7² - 4*2*5 = 49 - 40 = 9 = 3²

x' = (-7+3) / 3 = -4/3

x'' = (-7-3)/ 3 = -10/3

=> S = {-10/3 ; -4/3}

x(x-4) = 21

x² - 4x - 21 = 0

Δ = (-4)² - 4*(-21) = 16 + 84 = 100 = 10²

x' = (4 - 10)/2 = -3

x'' = (4+10)/2= 7

S = {-3 ; 7}