3^(4х-1)+3^(4х+1)>=80
3^(4x)/3^1 + 3^(4x) * 3^1 =>80
3^(4x)=t
t/3 + 3t => 80
t +3*3t => 80*3
10t => 240
t => 24
3^(4x) =>24
log 3(24) <= 4x
x =>1/4 log3(24)
x =>log 3 [24^(1/4)]
sin²15-cos²15=sin²15-(1-sin²15)=2sin²15-1=2=1-cos30-1=-cos30=
<span>10(х+2) +(у+2)+3=2(10х+у),т.е. Х=25</span>
80%от а это 8. 8×100÷25=32-это число b. 32×75:100=24.