Question

com a formula resolutiva resolva essa equaçao :
-x² +8x + 9 ?

Answer 1

-x²+8x+9=0 

Δ=b²-4,a.c

Δ=8²-4.(-1).9

Δ=64+36

Δ=100 

X=-b+-√Δ/2a

X=-8+-√100/-2

X=-8+-10/-2

X'=-8+10/-2  =  2/-2 = -1 

X''= -8-10/-2  =  -18/-2 = 9 

S=[-1,9] 

Answer 2

- x² + 8x + 9 = 0
a = - 1; b = 8; c = 9

Δ = b² - 4ac
Δ = 8² - 4.(-1).9
Δ = 64 + 4.9
Δ = 64 + 36
Δ = 100

x = - b +/- √Δ     =  - 8 +/- √100
      ---------------     ---------------------
            2a                     2.(-1)

x = - 8 + 10
      ------------ = 2/(-2) = - 1
          - 2

x = - 8 - 10
      ----------- = -18/(-2) = 9
         - 2

R.: x = - 1 e x = 9