A1+a1+9d=12 2a1+9d=12
a1+7d-a1-3d=4 4d=4 d=1 2a1=12-9=3 a1=1.5
s6=<span>((2a₁+d(n-1))/2)·n=(3+4/2)/2=5/2=2.5
an=1.5+1(n-1)=0.5+n</span>
<span>3х^2+1/4y^3
x = 1/3
</span>3х^2+1/4y^3 = 3*(1/3)^2+1/4y^3 = 3*1/9+1/4y^3 = (1/3)+(1/1)*3/4y^3 =
= (4/3)/4y^3
1200 кв. дм
Это очень просто)
<span>2d-4y</span> - <span>7d+3y </span> = <span>(2d-4y)*( 2d-3y)</span><span>-( 7d+3y )*( 2d-3y )</span> =