<span>(√х-2√ х-1)+(√ х+2√ х-1 )=</span><span>√х-2√ х-1+√ х+2√ х-1 =2√x=2√1,2007≈2*1,1≈2,2</span>
√9/10 + √144/10 - √81/10 = 3/√10 + 12/√10 - 9/√10 = ( 3 + 12 - 9) / √ 10 = 6/ √ 10 или 6√10 / 10
а) а12=4+2(12-1)=4+22=26, S12=((4+26)*12)/2=180
Х^2-3х-4=0
д=9-4×(-4)=25
х1=(3-5)/2=-1
х2=(3+5)/2=4