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z.43
a)
h = 4
Mamy
h/x = (10 - x)/h
czyli
4/x = (10 -x)/4
x*(10 - x) = 4*4 = 16
10x - x² = 16
x² - 10x + 16 = 0
Δ = (-10)² -4*1*16 = 100 - 64 = 36
√Δ = 6
x = [10 - 6]/2 = 4/2 = 2
10 - x = 10 - 2 = 8
a² = 4² + 8² = 16 + 64 = 80 = 16*5
a = √16*√5 = 4√5
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b² = 4² + 2² = 16 + 4 = 20 = 4*5
b = √20 = √4*√5 = 2√5
L - obwód Δ ABC
L = 10 + 4√5 + 2√5 = 10 + 6√5
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b) h = 4
AD = x
CD = h
Mamy
4² + (x +3)² = (2√13 )²
16 + x² + 6x + 9 = 4*13
x² + 6x + 25 - 52 = 0
x² + 6x - 27 = 0
Δ = 6² - 4*1*(-27) = 36 + 108 = 144
√Δ = 12
x = [-6 + 12]/2 = 6/2 = 3
zatem
b² = 4² + 3² = 16 + 9 = 25
b = √25 = 5
L - obwód Δ ABC
L = 3 + 5 + 2√13 = 8 + 2√13
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