<span>|7-x|=|2x-5|
</span>7-x=2x-5 и <span>7-x=-(2x-5)
</span>7-x=2x-5 и <span>7-x=-2x+5
</span>-3x=-12 и <span>x=-2
</span>x=4 и <span>x=-2</span>
Sin²a+cos²a=1
tga*ctga=1
sin²a+cos²a+tg²a*ctg²a=1+1=2
B3=-18, b1b6=486
b6=b3.q³,q³=b6/b3, q³=486/(-18)=-27
q=∛(-27), q=-3
b2=b3:q, b2=-18:(-3)=6, b1=b2:q, b1=6:(-2)=-3
b1+b2+b3=-3+6-18=-15