14 балла номер 161-163

$frac{(181^2-61^2)}{(319^2-209^2)} = frac{(181-61)(181+61)}{(319-209)(319+209)} = frac{20*242}{110*519} = frac{2*10*11*11}{11*10*173*3}= frac{22}{519}$
$frac{(38^2-17^2)}{(47^2-19^2)}= frac{(38-17)(38+17)}{(47-19)(47+19)} = frac{21*55}{28*66}= frac{1155}{1848} =0.625$

$(m+5)^2-(m-5)^2=(m^2+10m+25)-(m^2-10m+25)=20m$
$(x+y)^2-(x-y)^2=(x^2+2xy+y^2)-(x^2-2xy+y^2)=4xy$
$(x-6)^2-9x^2=(x^2-12x+36)-9x^2=-8x^2-12x+36$
$(6-n)^2-(n+6)^2=(36-12n+n^2)-(n^2+12n+36)=-24n$
$(2p-q)^2-(q+2p)^2=(4p^2-4pq+q^2)-(q^2+4pq+4p^2)=-8pq$
$4y^2-(y+3)^2=4y^2-(y^2+6y+9)=3y^2-6y-9$

$81x^2-9=0$
$9(9x^2-1)=0$
$9x^2-1=0$
$9x^2=1$
$x^2= frac{1}{9}$
$|x= sqrt{ frac{1}{9} }$
$|x= frac{1}{3}$
$|x=- sqrt{ frac{1}{9} }$
$|x=- frac{1}{3}$
Ответ: $frac{1}{3} ;- frac{1}{3}$

$-4y^2+16=0 4y^2-16=0 4(y^2-4)=0 y^2=4 |y= sqrt{4} |y=2 |y= -sqrt{4}|y=-2$
Ответ: $2;-2$