(5x-4)(5x+4)
(3x-4)^2
(b+5)^2
[x-4]=3
x=3+4 x=3-4
x=7 x=-1
1) -10+2х=26
2х=36
х=18
2)7у-9=40
7у=49
у=7
4cos²x -3 ≥ 0 ;
4*(1+cos2x)/2 -3 <span>≥ 0 ;
2 +2cos2x -3 </span>≥ 0 ⇔ cos2x <span>≥ 1/2
</span> 2πn -π/6 ≤ 2x ≤ π/6 + 2πn ,n∈Z
πn <span>-π/12 ≤ </span>x ≤ π/12 + πn ,n<span>∈Z
</span>
иначе x ∈[ πn -π/12 ; π/12 + πn ] ,n<span>∈Z</span>