Q. 1 A5.0( 2 Votes )

Solve the following quadratic equations by factorization method:

x2 + 10ix – 21 = 0

Answer :

x2 + 10ix – 21 = 0


Given x2 + 10ix – 21 = 0


x2 + 10ix – 21 × 1 = 0


We have i2 = –1 1 = –i2


By substituting 1 = –i2 in the above equation, we get


x2 + 10ix – 21(–i2) = 0


x2 + 10ix + 21i2 = 0


x2 + 3ix + 7ix + 21i2 = 0


x(x + 3i) + 7i(x + 3i) = 0


(x + 3i)(x + 7i) = 0


x + 3i = 0 or x + 7i = 0


x = –3i or –7i


Thus, the roots of the given equation are –3i and –7i.


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