Question

Vă rog, măcar primele trei subiecte.
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Answer 1

Răspuns:

Explicație pas cu pas:

I

1) A=l×h/2=20×1,7/2=1,7×10=17 cm²

2)A=70 cm²  l=10cm  ⇒h=2A/l=2×70/10=14 cm

3)A=BC×h1/2=12×5/2=6×5=30cm²

A=AC×h2/2     ⇒h2=2A/AC=2×30/4=30/2=15 cm

4)A Δdreptunghic=c1×c2/2=12×15/2=6×15=90 cm²

5)c2=2AΔdr/c1=2×350/7=2×50=100 cm

II

1)A=l²=1,2²=1,44 cm²

2)P=104 cm=4l      ⇒l=P/4=104/4=26 cm

3)A=l²=81 cm²   ⇒l=√A=9 cm  ⇒P=4l=4×9=36 cm

4)Acod=Aabcd:4

Aabcd=l²=64 cm²  ⇒Acod=64:4=16 cm²

III

1)A=L×l=9×18=162 cm²

P=2(L+l)=2(18+9)=2×27=54cm

2)P=2(L+l)=40   ⇒L+l=20

                            L=l+2       ⇒l+2+l=20      ⇒2l=18      ⇒l=9cm

IV

1)A=2×(BC×d(A, BC))/2=BC×d(A, BC)=18×13=234 cm²

2)A=l×h  =36 cm²     ⇒h=A/l=36/9=4 cm

V

1)A=d1×d2/2=6×14/2=6×7=42 cm²

2)A=48cm²      d1=6 cm  ⇒d2=2A/d1=2×48/6=2×8=16 cm

3)A=2AB×dist (C, AB)/2= AB×dist (C, AB)

AB=  A/AB×dist (C, AB)=40/4=10 cm

4)∡BAD=60° ⇒ ΔBAD echlateral  ⇒BD=AB=AD     AB=12 cm

VI

1)Lmijl=(B+b)/2=18 cm  si h=7 cm   ⇒A=Lmijl×h

A=18×7=126 cm²

2)Atrp=82 cm²=(B+b)×h/2    h=2A/(B+b)=2×820/(21+20)=2×2×41×10/41=40cm

3)Afghi=Aegh-Aefi=87 cm²-25 cm²=62 cm²

Aegm=Aegh/2=87cm²/2=43,5 cm²