To solve :(x-4+i)(x-4-i)(x-3).
Solution:
If you want to solve this , then it should be an equation like:
(x-4+i)(x-4-i)(x-3) = 0. Then you are solving for x , which is unknown and not i, which is known and is equal to (-1)^(1/2). Therefore, by zero product rule, any of the factors of the product (x-4+i)(x-4-i)(x-3) could be zero. So,
x-4i+i = 0 , or x-4-i = 0 or x=3 or
x=4-i or
=x=4+i or
x=3.
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If you want to find the product, then:
{(x-4 +i)(x-4 -i)}(x-3) = {(x-4)^2 - i^2}(x-3}............(1)
But as (a+b)(a-b) = a^2 - b^2 and used inside the flower bracket. Now, the expression at (1) becomes:
{(x^2-8x+16)-(-1)}(x-3), as x^2 = [(-1)(1/2)]^2 = 1. So, the expression is,
{x^2-8x+17}(x-3)
={x^2-8x+17}x + {x^2-8x+17}(-3)
=x^3-8x^2+17x -3x^2+24x-51
=x^3-(8+3)x^2+(17+24)x-51
=x^3-11x^2+41x-51.
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