1) 9^2+log₉2

2) 2cosx³+5cosx²-3cosx=0

3) log₃ (7-x) ≥ 2log₃7

9^2+log₉2 = 9²*9:^log (9) 2=81*2=162

2 (cosx) ³+5 (cosx) ²-3cosx=0

cosx=a

2a ³+5a²-3a=0

a (2a²+5a-3) = 0

a=0⇒cosx=0⇒x=π/2+πk, k∈z

2a²+5a-3=0

D=25+24=49

a1 (-5-7) / 4=-3⇒cosx=-3<-1 нет решения

а2 = (-5+7) / 4=1/2⇒cosx=1/2⇒x=+-π/6+2πk, k∈z

log₃ (7-x) ≥ 2log₃7

log (3) (7-x) ≥log (3) 49

{7-x>0⇒x<7

{7-x≥49⇒x≤7-49⇒x≤-42

x∈ (-∞; -42]