Q1 of 58 Page 106

Check whether the following are quadratic equation:

(x + 2)3 = 2x(x2 - 1)

(x + 2)3 = 2x(x2 - 1)

LHS = (x + 2)3 = x3 + 23 + 3 × x × 2(x + 2)


(∵(a + b)3 = a3 + b3 + 3ab(a + b))


= x3 + 8 + 6x2 + 12x


RHS = 2x3 - 2x


Equating LHS and RHS


x3 + 8 + 6x2 + 12x = 2x3 - 2x


- x3 + 6x2 + 14x + 8 = 0


which is not of the form ax2 + bx + c = 0


∴ it is not a quadratic equation.


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