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Ex 8.3, 4 (a) (a) Simplify 3x (4x – 5) + 3 and find its values for (i) x = 3 (ii) x = 1/23𝑥 (4𝑥−5)+3 = (3𝑥×4𝑥)−(3𝑥×5)+3 = 𝟏𝟐𝒙^𝟐−𝟏𝟓𝒙+𝟑 (i) For 𝒙=𝟑 Putting 𝑥=3 in expression 12𝑥^2−15𝑥+3 = 12(3)^2−15(3)+3 = (𝟏𝟐 × 𝟗)−(𝟏𝟓 × 𝟑) +𝟑 = 108−45 +3 = 108−42 = 𝟔𝟔 (ii) For 𝒙=𝟏/𝟐 Putting 𝑥=1/2 in expression 12𝑥^2−15𝑥+3 = 12(1/2)^2−15(1/2)+3 = 𝟏𝟐(𝟏/𝟐×𝟏/𝟐)− 𝟏𝟓/𝟐 +𝟑 = 12×(1/4)−15/2+3 = 𝟑−𝟏𝟓/𝟐+𝟑 = 6−15/2 = (6 × 2 − 15)/2 = (12 − 15)/2 = (−𝟑)/𝟐

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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 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.