28-4(3x+2)=5(2x-7)
28-12х-8=10х-35
-12х-10х=-35-28+8
-22х=-55
х=-55/(-22)=2.5
<span>х=2.5</span>
Tg t/(tg t + Ctg t) = ?
a)tg t = Sin t/Cos t
б) tg t + Ctg t = Sin t/Cos t + Cos t /Sin t = (Sin² t + Cos ²t)/Cos t Sin t= 1/Cos tSin t
в) Sin t/Cos t : 1/Cos tSin t = Sin t /Cos t ·Cos t Sin t /1= Sin²t
(х-1)(х+2)(х+10)=0
x - 1 = 0 x + 2 = 0 x + 10 = 0
x = 1 x = - 2 x = -10