Q22 of 82 Page 4

Solve for x: . (CBSE 2016)



…(squaring both sides)


6x + 7 = 4x2 – 28x + 49


⇒ 0 = 4x2 – 28x – 6x – 7 + 49


⇒ 4x2 – 34x + 42 = 0


⇒ 2x2 – 17x + 21 = 0


⇒ 2x2 – 14x – 3x + 21 = 0


⇒ 2x(x – 7) –3(x – 7) = 0


⇒ (x – 7) (2x – 3) = 0


⇒ x – 7 = 0 or 2x – 3 = 0


⇒ x = 7 or x = 3/2


checking: when x = 7, in (i),



√49 – (14 – 7) = 0


7 – 7 = 0 True


When x = 3/2, in (i)




⇒ 4 + 4 ≠ 0 false


so, x = 7 is answer.

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