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课程 8 · 年级 7–9
Functions and graphs
📖 课程
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🎯 测验——选择翻译
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✅ 本课已完成
A function is a machine: x in, y out. The linear function y = kx + b draws a line: k is the slope, b the y-intercept. Taxi price: y = 3·x + 10 — 10 € pickup plus 3 € per km. Reading the graph shows everything: where expensive, where cheap, where zero.
- ●y = 2x: line through zero, each step right = 2 up
- ●y = −x + 5: falling line, starts at 5
- ●k > 0 rises, k < 0 falls, k = 0 — flat
📱 A phone plan is a function: 20 € + 0.5 €/GB. Comparing two plans means comparing two lines.