100б+100к+100с=150б+150к+50с
50с-50к=50и
с-к=б
150б+150к+50с=200б+50к+60с
100к-10с=50б
2к-0.2с=б=с-к
1.2с=3к
с=30/12к=2.5к
1) x^2-y^2= (x+y)(x-y)
2) p^2-4= (p+2)(p-2)
3) c^2-b^2= (c+b)(c-b)
4) 9-a^2= (3+a)(3-a)
5) 16-x^2= (4+x)(4-x)
6) y^2-25= (y+5)(y-5)
7) 25x^2-y^2= (5x+y)(5x-y)
Вот и все!!!
5ctg(3π+π/2+a)/4ctga=5ctg(π/2+a)/4ctga=-5tga/4ctga=-5/4*tg²a
a=5π/4
-5/4*tg²(π+π/4)=-5/4*tg²π/4=-5/4*1=-1,25