1) х1+х2=7/5
-2+х2=7/5
х2=17/5
2)х1*х2=k/5
-2*17/5=k/5
k=-34
<span>3х>12 x</span>∈(4;+∞)<span>
</span><span>2х≤12 x</span>∈(-∞;6]
x∈(4;6]
x=5;6
x(sr)=(5+6)/2=5.5
-sin²b*cos²b+cos²b-cos⁴b=cos²b*(-sin²b)+cos²b*1+cos²b*(-cos²b)=cos²b(-sin²b+1-cos²b)=cos²b*0=0