Q2 of 83 Page 90

Find the roots of the following equations by the method of perfect square:

3x2 + 7x — 20 = 0

Multiplying the whole equation by 12, we get –

⇒ 36x2 + 84x — 240 = 0


⇒ 36x2 + 84x + 49 – 289 = 0



⇒ (6x + 7)2 – 172 = 0


⇒ (6x + 7 – 17)(6x + 7 + 17) = 0


⇒ (6x – 10)(6x + 24) = 0


⇒6x – 10 = 0 or 6x + 24 = 0




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