Răspuns:
Explicație pas cu pas:
a) x²-6x-31 = 0
a = 1 ; b = -6 ; c = -31
Δ = b²-4ac = (-6)²-4·1·(-31) = 36+124 = 160
√Δ = √160 = 4√10
x₁,₂ = (-b±√Δ)/2a = (6±4√10)/2 = 3±2√10
x₁ = 3-2√10 ; x₂ = 3+2√10
b) 4x²-13x-12 = 0
a = 4 ; b = -13 ; c = -12
Δ = (-13)²-4·4·(-12) = 169+192 = 361
√Δ = √361 = 19
x₁,₂ = (-b±√Δ)/2a = (13±19)/8
x₁ = -6/8 => x₁ = -3/4
x₂ = 32/8 => x₂ = 4
c) 5x²+9x-2 = 0
a = 5 ; b = 9 ; c = -2
Δ = 9²-4·5·(-2) = 81+40 = 121
√Δ = √121 = 11
x₁,₂ = (-9±11)/10
x₁ = -20/10 => x₁ = -2
x₂ = 2/10 => x₂ = 1/5
#copaceibrainly
