1
(√x-2√y)(√x+2√y)/(√x+2√y) -(√x+2√y)(x-2√(xy)+4y)/[(√x-2√y)(√x+2√y)]=
=(√x-2√y)-(x-2√(xy)+4y)/(√x-2√y)=[(√x-2√y)²-(x-2√(xy)+4y)]/(√x-2√y)=
=(x-4√(xy)+4y-x+2√(xy)-4y)/(√x-2√y)=-2√(xy)/(√x-2√y)
x=1/2,y=50
(-2*1/√2*5√2):(1/√2-2*5√2)=-10:(-19/√2)=10√2/19
2
19/2-√14+9√70/[√70(√14-√5)]-√5=19/2-√14+9/(√14-√5)-√5=
=19/2-√14+9(√14+√5)/[(√14-√5)(√14+√5)]-√5=
=19/2-√14+9(√14+√5)/(14-5)-√5=19/2-√14+√14+√5-√5=19/2=9,5
3
√(4+√5)²+√(4-√5)²=|4+√5|+|4-√|=4+√5+4-√5=8
=19/2-√14