6 + (3х - 2)/5 = х общ.знаменатель = 5
30 + 3х - 2 = 5х
3х - 5х = - 30 + 2
-2х = - 28
2х = 28
х= 14
=14b+b²-49+b²-14b+49=2b²
если b=-1/3, то 2b²=2*(-1/3)²=2*1/9=2/9
3x^3y^3-xy+4xy^2-3x^3y^3+2xy+2xy^2=-xy+4xy^2+2xy+2xy^2=xy+4xy^2+2xy^2=xy+6xy^2=xy(1+6y)
A7=21 s7=105 s7=(2а1+6d)*7/2=7(a1+3d)=105
a1+6d=21
a1+3d=15
3d=21-15=6 d=2 a1=21-6d=21-12=9