Last updated at Dec. 8, 2016 by Teachoo

Transcript

Example 9 Find the roots of 4x2 + 3x + 5 = 0 by the method of completing the square. 4x2 + 3x + 5 = 0 Dividing by 4 4๐ฅ2/4+3๐ฅ/4+5/4=0 x2 + 3๐ฅ/4+5/4=0 We know that (a + b)2 = a2 + 2ab + b2 Here, a = x & 2ab = 3๐ฅ/4 2xb = 3๐ฅ/4 2b = 3/4 b = 3/4ร1/2 b = 3/8 Now, in our equation x2 + 3๐ฅ/4+5/4=0 Adding and subtracting (3/8)^2 x2 + 3๐ฅ/4+5/4+(3/8)^2โ(3/8)^2=0 x2 + 3๐ฅ/4+(3/8)^2+5/4โ(3/8)^2=0 (๐ฅ+3/8)^2+5/4โ(3/8)^2=0 (๐ฅ+3/8)^2=(3/8)^2โ5/4 (๐ฅ+3/8)^2=9/64โ5/4 (๐ฅ+3/8)^2=(9 โ 5(16))/64 (๐ฅ+3/8)^2=(9 โ 80)/64 (๐ฅ+3/8)^2=(โ71)/64 Since square of any number cannot be negative So, answer does not exist

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.