Resposta:
4ײ - 20× +9= 0
= (-20)² - 4.4.9
= 400 - 144
= 256
x= 20+ - 256/ 2.4
x= 20+ - 16/ 8
x1 = 20+ 16/ 8
x1= 36 / 8
x1= 4,5
x2= 20 - 16 / 8
x2= 4/ 8
x2= 0,5
