x^2+4x-12=0

D=4^2+48=64

x1=(-4+8)/2=2

x2=(-4-8)/2=-6

x^2-10x+16=0

D=100-64=36

x1=(10+6)/2=8

x2=(10-6)/2=2

x^2+8x-7=0

D=64-28=36

x1=(-8+6)/2=-1

x2=(-8-6)/2=-7

25x^2-10x-3=0

D=100+300=400

x1=(10+20)/2=15

x2=(10-20)/2=-5

x^2-3x-10=0

D=9+40=49

x1=(3+7)/2=5

x2=(3-7)/2=-2

429

2) х2 + 4 - 12 = 0

Д = в2 - 4ас

Д = 16 + 48 = 64

Д = 8