Odpowiedzi

2010-03-28T20:26:01+02:00
A - długość
b - szerokość
d - przekątna

Obw = 42
Obw = 2a + 2b

a = 3
b = 4

Obw = 42
4a = 3b
2a + 2b = 42
4a = 3b
2a = 42 - 2b /:2
4a = 3b
a = 21 - b
4 *(21 - b) = 3b
a = 21-b
84 - 4b = 3b
a = 21 - b
84 = 3b + 4b
a = 21 - b
84 = 7b /:7
a = 21 - b
b = 12
a = 21 - 12
b = 12
a = 9
b = 12

d = √a² + √b²
d = √81 + √144
d = √225
d = 15cm
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2010-03-28T20:27:34+02:00
O=2a+2b

42=2a+2b
a/b=3/4

42=2a+2b
a=3/4b

42=2*3/4b+2b
42=3/2b+2b
42=7/2b
b=42*2/7
b=12 cm

a=3/4*12
a=9 cm

d=√(a²+b²)
d=√(9²+12²)
d=√(81+144)
d=√225
d=15 cm
2010-03-28T20:33:53+02:00
Ob = 2a+2b
2a+2b = 42 /:2
a+b = 21
a = 21-b

a/b = 3/4
3b = 4a /:3
b = 4a/3
b= 4/3a

a = 21-b
a = 21-4/3a
a+4/3a = 21
7/3 a = 21 /:7/3
a = 3*3
a = 9

b = 4/3*9 = 12
z tw. Pitagorasa
d² = 9²+12²
d² = 81+144
d² = 225
d = √225
d = 15

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