1) ( а + 1 )( а - 1 ) = а^2 - 1
2) ( а^2 - 1 )( а^2 + 1 ) = а^4 - 1
3) ( 9 + а^2 )^2 = 81 + 18a^2 + a^4
4) a^4 - 1 - ( 81 + 18a^2 + a^4 ) = a^4 - 1 - 81 - 18a^2 - a^4 = - 82 - 18a^2
5) a = 1/3
- 82 - 18 • 1/9 = - 82 - 2 = - 84
(6k)^2+(3m)^2+2*6k*3m=(6k+3m)^2.
<span>7х+8=11-2х
7х+2х=11-8
9х=3
х=1/3
</span>
1) 8(х-10)²-11(х+5)²=-3х²-170х +1600
8(х² -20х+100)-11(х²+10х+25)=-3х²-17-х+1600
8х²-160х+800-11х²-110х-275=-3х²-17-х+1600
-3х²-270х+525=-3х² - 170х+1600
-270х+525= -170х+1600
-100х=1075
2)2,5(16+8х+х²)+7(25-х²)=295-4,5х²
40+20х+2,5х²+175-7х²=295-4,5х²
215+20х-4,5х²=295-4,5х²
215+20х=295
20х=80
х=4