Question

x² + 2x - 15 =0
calcule

Answer 1

4-4.1.-15<br />4+60<br />64<br />-2+-√69<br /> 2<br />-2+8 +2-8<br /> 2 2<br /><br /><br /><br /><br /> -2-8=-5 -2+8=+3 2 2

Answer 2

x² + 2x - 15 = 0
a = 1; b = 2; c = - 15

Δ = b² - 4ac
Δ = 2² - 4.1.(-15)
Δ = 4 + 60
Δ = 64

a = 1; b = 2; c = - 15

x = - b +/- √Δ      - 2 +/- √64
     -------------- = ----------------- 
             2a                2.1

x = - 2 + 8
      ---------  = 6/2 = 3
         2

x = - 2 - 8
     ----------  =  - 10/2 = - 5
          2

R.: x = 3 e x = - 5