=8(cosx-cos2x)=8(cosx-2cos^x+1)=8(3/4-2*9/16+1)=8*10/16=5
1/b*x^2=2*x-b
x^2=2*b*x-b^2
x^2-2*b*x+b^2=0
D=4*b^2-4*b^2=0
x=2*b/2=b
x=b
(6 1/2 - 0,9) : 1/10
((2 * 6 + 1)/2 - 9/10) : 1/10 = (13/2 - 9/10) : 1/10 = ((13*5-9)/10) : 1/10 = 56/10* 10 = 56
x² +px +q =0 , x₁ = 9 ; x<span>₂ =11 </span>
{ p = -(x₁ + x₂) ; q = x₁*x<span>₂
</span>===
x² -( -9 +11) x + (-9)*81 = 0⇔ x² -2x -99 =0.
ответ : x² -2x -99 =0 ; || a(<span>x² -2x -99 =0) ; </span>a ≠0 ||
(1/7)^-2=x+7 (основное свойство логарифма)