Ex 8.3, 4 (a) - Chapter 8 Class 8 Algebraic Expressions and Identities

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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