№418

3) 4x^2+4x+1=0

a=4, b=4, c=1

D=4^2-4*1*4=16-16=0

x=(-4±0)/8=-1/2

4) 25-10x+x^2

a=1, b=-10, c=25

D=-10^2-4*1*25=100-100=0

x=(10±0)/2=5

№419

1) 101^2-202*81+81^2=(101-81)^2=400

2) 37^2+126*37+63^2=(37+63)^2=10000

3) (48^2+2*48*18+18^2)/(48^2-18^2) = ((48+18)^2)/(48-18)(48+18) = (48+18)/(48-18) = 66/30=11/5=2,2

4) (85^2-17^2)/(85^2+2*85*17+17^2) =(85-17)(85+17)/(85+17)^2=(85-17)/(85+17)=68/102=2/3