Question

x³+2x²-3x+21, if x = (1+2i)​

Answer 1

1

Step-by-step explanation:

x

3

+2x

2

−3x+21 if x=1+2i

(x−1)

2

=(2i)

2

x

2

−2x+1=−4

x

2

−2x+5=0

∴x

3

+2x

2

−3x+21

=x(x

2

−2x+5)+4x

2

−8x+21

=0+4x

2

−8x+21

=4(x

2

−2x+5)+1

=0+1

=1

Value is 1.

Answer 2

Refer the attachment for the answer