C = 0,1x² + 2X + 50
C = 0,1x² + 2x + 50 = 6,5x
C = 0,1x² + 2x - 6,5x + 50 = 0
C = 0,1x² - 4,5x + 50 = 0
C = 1/10x² - 4,5x + 50 = 0
C = x² - 45x + 500 = 0
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∆ = b² - 4ac
∆ = (-45)² - 4(1)(500)
∆ = 2025 - 2000
∆ = 25
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x = -b ± √∆ /2a
x = -(-45) ± √25 / 2(1)
x = 45 ± 5 / 2
x' = 45+5/2
x' = 25
x'' = 45-5/2
x'' = 20
Resposta:
20 ≤ x ≤ 25