х² + 3х - 40 = ( х - 5 ) ( х + 8 ).
D = 9 - 4 × 1 × (-40) = 9 + 160 = 169 > 0. 13.
х1 = ( -3 + 13 ) / 2 = 10/2 = 5.
х2 = ( -3 - 13 ) / 2 = -16/2 = -8.
Удачи)))
1)x^2+3x-40=(x+8)(x-5)
2) x^2+3x-40
D = b2 - 4ac = 32 - 4·1·(-40) = 9 + 160 = 169
x1=-3 - √169/2=-8
x2=-3 + √169/2=5
