120+90+х+х•3=157×2
210+4х=314
4х=314-210
4х=104
х=104:4
х=26кг-гречка
26×3=78кг-манка
<span>4*10000+6*1000+2*100+2*10+3=40000+6000+200+20+3=46223</span>
Sin2x = cos2x - sin^2x + 1
2sinxcosx = cos^2x -sin^2x + cos^2x
sin^2x + 2sinxcosx - 2cos^2x = 0
Разделим обе части ур-я на cos^2x не = 0.
tg^2x + 2tgx - 2 = 0
1) tgx = -1 - V3 ===> X1 = arctg(-1 - V3)
2) tgx = -1 + V3 ===> X2 = arctg(-1 + V3)