P❍➪◆● ●❉✫✣❚ ❍❯❨➏◆ ❍➶❈ ▼➷◆ ❚❘×❮◆● ✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳✳ ✣➋ ❑■➎▼ ❚❘❆ ●■Ú❆ ❍➴❈ ❑➐ ■ ◆❿▼ ❍➴❈✿ ✷✵✷✷ ✲ ✷✵✷✸ ✖✖✖✖✖✖✖✖✖✖✖✖ ▼➷◆✿ ❚❖⑩◆ ✲ ▲❰P✿ ✽ ✣➋ ❚❍❆▼ ❑❍❷❖ ❚❤í✐ ❣✐❛♥ ❧➔♠ ❜➔✐✿ ✾✵ ♣❤ót ❇➔✐ ✶ ✭✷✱✵ ✤✐➸♠ ✮✳ ❚❤ü❝ ❤✐➺♥ ♣❤➨♣ t➼♥❤ ✈➔ rót ❣å♥✿ ❛✮ (x − 2)(x + 1) − x + ❜✮ (x + 2) − x − 2x ❇➔✐ ✷ ✭✷✱✵ ✤✐➸♠ ✮✳ P❤➙♥ t➼❝❤ ✤❛ t❤ù❝ t❤➔♥❤ ♥❤➙♥ tû✿ ❛✮ 5x − 10xy ❜✮ x − 6x + ❝✮ x − y + 5x − 5y ❇➔✐ ✸ ✭✷✱✵ ✤✐➸♠ ✮✳ ❚➻♠ x✱ ❜✐➳t✿ ❛✮ 5x(x − 5) − 5x = 50 ❜✮ (x + 3) − 2x − = ❇➔✐ ✹ ✭✵✱✺ ✤✐➸♠ ✮✳ ❚➼♥❤ ✤ë ❞➔✐ ✤♦↕♥ t❤➥♥❣ M N tr➯♥ ❤➻♥❤ ✈➩ s❛✉✿ 2 2 2 2 ❇➔✐ ✺ ✭✵✱✺ ✤✐➸♠ ✮✳ ❍❛✐ ❜↕♥ ▲❛♥ ✈➔ ❇➻♥❤ ❝❤ì✐ ❜➟♣ ❜➯♥❤✳ ❇✐➳t ❝❤✐➲✉ ❝❛♦ ❝õ❛ trö ❜➟♣ ❜➯♥❤ ❧➔ ✱ ❦❤♦↔♥❣ ❝→❝❤ ❝õ❛ ❇➻♥❤ ✤➳♥ ♠➦t ✤➜t ❧➔ 30cm✳ ❍ä✐ ▲❛♥ ❝→❝❤ ♠➦t ✤➜t ❜❛♦ ♥❤✐➯✉ cm❄ 40cm ❇➔✐ ✻ ✭✷✱✵ ✤✐➸♠ ✮✳ ❈❤♦ t❛♠ ❣✐→❝ ABC ♥❤å♥ (AB < AC)✳ ●å✐ M ✱ N ❧➛♥ ❧÷đt ❧➔ tr✉♥❣ ✤✐➸♠ ❝õ❛ AB✱ AC ✳ ❛✮ ❈❤ù♥❣ ♠✐♥❤✿ ❚ù ❣✐→❝ BM N C ❧➔ ❤➻♥❤ t❤❛♥❣✳ ❜✮ ❚r➯♥ t✐❛ ✤è✐ ❝õ❛ t✐❛ N M ❧➜② ✤✐➸♠ K s❛♦ ❝❤♦ N M = N K ✳ ❈❤ù♥❣ ♠✐♥❤✿ ❚ù ❣✐→❝ BCKM ❧➔ ❤➻♥❤ ❜➻♥❤ ❤➔♥❤✳ ❇➔✐ ✼ ✭✶✱✵ ✤✐➸♠ ✮✳ ❈❤♦ x + y = ✈➔ x + y = 10✳ ❚➼♥❤ ❣✐→ trà ❜✐➸✉ t❤ù❝✿ M = x + y ✳ 2 3