x²+9=(x-3)²
x²+9= x²-6x+9
6x=0
x=0
x²+12=(x+6)²
x²+12= x²+12x+36
12x=-24
x= -2
x²-11x+30=0
D=121-120= 1
x1= (11-1)/2= 5
x2= (11+1)/2= 6
x²-9x+8=0
D=81-32= 49
x1= (9-7)/2= 1
x2= (9+7)/2= 8
x=(2x-21)/x+12
x≠-12
x²+12x=2x-21
x²+10x+21=0
D= 100-84= 16
x1= (-10-4)/2= -7
x2= (-10+4)/2= -3
x²+9=(x-3)²
x²+9= x²-6x+9
6x=0
x=0
x²+12=(x+6)²
x²+12= x²+12x+36
12x=-24
x= -2
x²-11x+30=0
D=121-120= 1
x1= (11-1)/2= 5
x2= (11+1)/2= 6
x²-9x+8=0
D=81-32= 49
x1= (9-7)/2= 1
x2= (9+7)/2= 8
x=(2x-21)/x+12
x≠-12
x²+12x=2x-21
x²+10x+21=0
D= 100-84= 16
x1= (-10-4)/2= -7
x2= (-10+4)/2= -3