Question

4) resolva as equacoes do 2 grau identifique os coeficientes e determine as raízes existir.C) x²+2x-8=0D)x²-5x+8=0E)2x²-8x+8=0F)x²-4x-5=0G)-x²+x+12=0I)-x²+6x-5=0J)6x²+x-1=0K)3x²-7x+2=0L)2x²-7x+2=0M)4x²+9=12xN)x²=x+12O)2x²=-12x-18P)x²+9=4xQ)25x²=20x-4R)2x=15-x²S)x²+3x-6=-8T)x²+x-7=5U)4x²-x+1=x+3x²V)3x²+5x=-x-9+2x²X)4+x (x-4)=xZ)x (x+3)-40=0

Answer 1

a-
x² + 2x - 8 = 0
a = 1, b = 2, c = -8
delta = b² - 4 . a . c
delta = 2² - 4 . 1 . (-8)
delta = 4 - 4 . (-8)
delta = 4 + 32
delta = 36

-b + ou - raiz de delta (36), sobre 2.a 
x' = -2 + 6 / 2 = 2
x" = -2 - 6 / 2 = -4