Ex 9.5, 5 - Show that (i) (3x + 7)^2 - 84x = (3x - 7)^2 (ii) (9p - 5q)

 

 

 

  1. Chapter 9 Class 8 Algebraic Expressions and Identities
  2. Serial order wise

Transcript

Ex 9.5, 5 Show that. (i) (3π‘₯+7)^2βˆ’84π‘₯=(3π‘₯βˆ’7)^2 Solving LHS (3π‘₯+7)^2βˆ’84π‘₯ = (3π‘₯)^2+(7)^2+ 2(3π‘₯)(7)βˆ’84π‘₯ = 9π‘₯^2+49+42π‘₯βˆ’84π‘₯ = 9π‘₯^2+49βˆ’42π‘₯ (π‘Ž+𝑏)^2=π‘Ž^2+𝑏^2βˆ’2π‘Žπ‘ Putting π‘Ž = 3π‘₯ & 𝑏 = 7 = (3π‘₯)^2+(7)^2+ 2(3π‘₯)(7)βˆ’84π‘₯ = 9π‘₯^2+49+42π‘₯βˆ’84π‘₯ = 9π‘₯^2+49βˆ’42π‘₯ Solving RHS (3π‘₯βˆ’7)^2 (π‘Žβˆ’π‘)^2=π‘Ž^2+𝑏^2βˆ’2π‘Žπ‘ Putting π‘Ž = 3π‘₯ & 𝑏 = 7 = (3π‘₯)^2+(7)^2βˆ’2(3π‘₯)(7) = (3^2Γ—π‘₯^2 )+49βˆ’(2Γ—3Γ—7)π‘₯ = 9π‘₯^2+49βˆ’42π‘₯ Thus LHS = RHS Hence proved

About the Author

Davneet Singh's photo - Teacher, Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.