1
4^x-6*2^x+8≤0
2^x=a
a²-6a+8≤0
a1+a2=6 U a1*a2=8
a1=2 U a2=4
2≤a≤4
2≤2^x≤4
1≤x≤2
x∈[1;2]
2
sinx(sinx-cosx)=0
sinx=0⇒x=πn,n∈z
sinx-cosx=0/cosx
tgx-1=0⇒ygx=1⇒x=π/4+πk,k∈z
3
2cos²x-5cosx+2=0
cosx=a
2a²-5a+2=0
D=25-16=9
a1=(5-3)/4=1/2⇒cosx=1/2⇒x=+-π/3+2πn,n∈z
a2=(5+3)/4=2⇒cosx=2>1 нет решения