Решите неравенство: 4(2x+3) - 3 ≤ 6x - 7

8х+12-3≤6х-7

8х-6х≤-7-12+3

2х≤-16

х≤-8      

8x + 12 -3 ≤ 6x - 7

8x +9 > 6x - 7

f(x)=4x-1/x3

f '(x)=x+3/x^4

cosacosb=1/2(cos(a-b)+cos(a+b)

2cos20cos40=2*1/2(cos(20-40)+cos(20+40)=cos20+cos60

cos20+cos60-cos20=cos60=1/2