Х⁴-2х²+1=(х²-1)²
4-20с+25с²=2²-20с+(5с)²=(2-5с²)²
3х-4у=-7 [*2
2х+5у=3 [*(-3)
....
6х-8у=-14
-6х-15у=-9
_________
-23у=-23
у=-1
...
у=1
2х+5у=3
...
у=1
2х=3-5
...
у=1
2х=-2
...
у=1
х=-1
1)2√175-3=4<span>√43
2)28+2=</span><span>√30
3)3</span><span>√7-60
</span>
79*81= <span> (80-1)(80+1)= 80</span>²-1²= 6400-1=6399
Y=3x-5;
y=-5x+11;
3x-5=-5x+11;
8x=16;
x=2; y=1;
Ответ: (2;1).