Question

11 и 12 пожалуйста................?

Answer 1

11)ΔВОС подобен ΔАОD⇒BC/AD=k
S(BOC)/S(AJD)=k²
32/S(AOD)=16/81
S(AOD)=32*81/16=162
h(BOC)=2S(BOC)/BC=2*32/4=16
h(AOD)=2S(AOD)/AD=2*162/9=36
hтр=h(BOC)+h(AOD)=16+36=52
Sтр=(BC+AD)*h/2=(4+9)*52/2=13*26=338
12)a2+a6=14⇒2a1+6d=14⇒a1=7-3d
a3*a8=76⇒(a1+2d)(a1+7d)=76⇒(7-d)(7+4d)=76
49+28d-7d-4d²-76=0
4d²-21d+27=0
D=441-432=9
d1=(21-3)/8=9/4⇒a1=7-3*9/4=1/4 не удов усл
d2=(21+3)/8=3⇒a1\7-9==2