Question

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Answer 1

Răspuns:

17. a)Pabcd=2(AB+BC)=2(4+2,5)=2•6,5=13cm.

b)Pabcd=2(CD+BC)=2(130+50)=2•180=360cm.

18. Pabcd=42cm=>

AB=7cm=>

BC=?cm.

=>Pabcd=2(AB+BC)=>42=2(7+BC)=14+2BC=>2BC=42-14=28=>2BC=28=28÷2=14=>BC=14cm.

19. Pabcd=30cm

AB=5+AD=5+5=10=>AB=10cm.

=>Pabcd=2(AB+AD)=>30=2(5+AD+AD)=>30=2(5+2AD)=>30=10+4AD=>4AD=30-10=20=>4AD=20=20÷4=5=>AD=5cm.

20. Pabcd=42cm.

AB=2AD=2×7=14=>AB=14cm.

=>Pabcd=2(AB+AD)=>42=2(AD+2AD)=>42=2×3AD=6AD/6=>AD=7cm.

16. a)∢B=56°

∢C=124°

∢D=56°

b)∢A=∢C=140°

∢A+∢B+∢C+∢D=360°

140°+2∢B+140°=360°

280°+2∢B=360°

2∢B=360°-280°=80°=>∢B=80°÷2=40°=>

=>∢B=∢D=40°

∢ABD=40°-23°=17°

∢ABD=17°

∢ABC=40°

c),d) te descurci in continuare.Bafta!