log(7) (2x-6) <= log(7) (1/7)
<span>x^3-64x=0
x^3=64x
x=8
Проверка:
8^3=64*8
512=512</span>
4(cos20-sin20)/(√2sin25)=4(cos20-cos70)/(√2sin25)
=-8*sin45*sin(-25)/(√2sin25)=4√2sin25/(√2sin25)=4
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sin20=sin(90-70)=cos70
cosa-cosb=-2sin[(a+b)/2*sin(a-b)/2]
X(x-4)-5(4-x)=x(x-4)+5(x-4)=(x-4)(x+5)
А) 7xy^2-14x^2 =7х(у^2-2x)
б) 5a-ab+5c-cb=(5а-аb)+(5с-сb)=а(5-b)+с(5-b)=(а+с)(5-b)
в)25x-x^3=х(25-х^2)=x(5+x)(5-x)