F(x)=x^2-9
a)f(6)=6^2-9=27
f(-0,5)=(-0,5)^2-9=-8,75
б)f(x)=-9=x^2-9
x^2-9=-9
x^2=0
x=0
При х=0 <span>f(x)=-9
_____________
</span><span>f(x)=7=x^2-9
</span>x^2-9=7
x^2=9+7
x^2=16
x=+-4
При х=4 или х=-4 <span>f(x)=7</span>
с^9:с^4*c*c^2=с^9:(с^4*c*c^2)=с^9:c^7=c^2
81*3^x>1\9
3^4*3^x>3^-2
4+x>-2
x>-6
ответ<span>(-6;+беск.)</span>