Ex 9.5, 5 Show that. (i) (3𝑥+7)^2−84𝑥=(3𝑥−7)^2 Solving LHS (3𝑥+7)^2−84𝑥 = (3𝑥)^2+(7)^2+ 2(3𝑥)(7)−84𝑥 = 9𝑥^2+49+42𝑥−84𝑥 = 9𝑥^2+49−42𝑥 (𝑎+𝑏)^2=𝑎^2+𝑏^2−2𝑎𝑏 Putting 𝑎 = 3𝑥 & 𝑏 = 7 = (3𝑥)^2+(7)^2+ 2(3𝑥)(7)−84𝑥 = 9𝑥^2+49+42𝑥−84𝑥 = 9𝑥^2+49−42𝑥 Solving RHS (3𝑥−7)^2 (𝑎−𝑏)^2=𝑎^2+𝑏^2−2𝑎𝑏 Putting 𝑎 = 3𝑥 & 𝑏 = 7 = (3𝑥)^2+(7)^2−2(3𝑥)(7) = (3^2×𝑥^2 )+49−(2×3×7)𝑥 = 9𝑥^2+49−42𝑥 Thus LHS = RHS Hence proved

Made by

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.

Class 6

Class 7

Class 8

Class 9

Class 10

Class 11

Class 12

Courses

Popular