4х+5х-4=0
-6х^2+х+3=0
15х-х^2=0
7х^2=0
3х-х

1. 4х+5х-4=0

9х = 4

х = 4/9

ответ: 4/9

2. -6х^2+х+3=0

D = 1 + 72 = 73

3. 15х-х^2=0

х(15 - х) = 0

1)х = 0

2)15 - х = 0

х = 15

ответ: 0; 15

4. 7х^2=0

х = 0

ответ: 0

5. 3х-х^2+19=0

-х^2 + 3х + 19 = 0

D = 9 + 76 = 85