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Ex 7.1, 8 Find the values of y for which the distance between the points P (2, – 3) and Q (10, y) is 10 units. Let the points be P (2, – 3) & Q (10, y) Given that PQ = 10 units By distance formula PQ = √((𝑥2 −𝑥1)2+(𝑦2 −𝑦1)2) x1 = 2, y1 = −3 x2 = 10, y2 = y PQ = √(( 10 −2)2+(𝑦−(−3))2) 10 = √((8)2+(𝑦+3)2) Squaring both sides (10)2 = (√((8)2+(𝑦+3)2))2 (10)2 = (8)2 + (y+ 3)2 100 = 64 + (y+ 3)2 100 = 64 + y2 + 32 + 2 × 3 × y 100 = 64 + y2 + 9 + 6y 0 = y2 + 6y + 64 + 9 − 100 0 = y2 + 6y – 27 y2 + 6y – 27 = 0 y2 + 9y – 3y – 27 = 0 y(y + 9) – 3(y + 9) = 0 (y – 3) (y + 9) = 0 Hence, y = 3 or y = −9 is the solution

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.