1)5x+(7y-x)-(3x+7x)
<span>5х+7у-х-3х-7у</span>
<span>х </span>
2) 6(a-2)-3(2a-5)
<span>6а-12-6а+15</span>
<span>3</span>
2sinx*cosx*sinx/cosx=1
2Sin²x=1
sin²=1/2
sinx=-1√2⇒x=-π/4+2πk U x=-5π/4+2πk,k∈z
sinx=1/√2⇒x=π/4+2πk U x=3π/1+2πk,k∈z
2(3-х)(х-7)>0
(3-х)(х-7)>0
(3-х)(х-7)=0
корни: x1=3 x2=7