1) Cos5x-cos3x=0
-2sin4xsinx=0
sin4x=0⇒4x=πn⇒x=πn/4,n∈z -общее
sinx=0⇒x=πk,k∈x
2) lgx + 2lg2 = 0.5lg49 - lg5
x>0
lg(4x)=lg(√49/5)
4x=1,4
x=1,4:4
x=0,35
(x^3 + 8) / (x^2 -2x+4) = (x+2)*(x^2 -2x+4) / (x^2 -2x+4) = (x+2)
7m(m³ – 8m² +9)=7m⁴-56m³+63m;
(x - 2)(2x+3)=2x²-4x+3x-6=2x²-x-6;
(3m – 4n)(5m + 8n)=15m²-20mn+24mn-32n²=15m²+4mn-32n²;
(y+3)(y² + y – 6)=y³+3y²+y²+3y-6y-18=y³+4y²-3y-18;