4) 3х2+5х=0
6) 9х2-4=0

3х2+5х=0x*(3x+5)= 0 x=0 3x+5=0 , x = - 5/3x1=0 ,x2= - 5/3 9х2-4=09x²=4x² = 4/9x= + 2/3 , - 2/3x1= 2/3 , x2=-2/3