Question

if 2 X equal to 3 + 5i then what is the value of 2 x cube + 2 x square - 7 x + 72..............






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plz answer this question.












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Answer 1

Answer:

Step-by-step explanation:

2x = 3 + i5 . . . . . . . . . . . . . . . . . . . . .(1)

x = 3/2 + i5/2 . . . . . . . . . . . . . . . . . . (2)

-7x = -21/2 - i35/2 . . . . . . . . . . . . . . . . . . . . . . .(3)

squaring both sides of (2)

x^2 = (-4 + i 15/2) . . . . . . . . . . . . . (4)

2x^2 = (-8 + i15) . . . . . . . . . . . . . . . . . . . . . . . . .(5)

x^3 = (-4 + i15/2)(3/2 + i5/2) . . . . . .(6)

x^3 =- 99/4 + i5/4 . . . . . . . . . . . . . . (7)

2x^3 = -99/2 + i5/2 . . . . . . . . . . . . . . . . . . . . . .(8)

f(x) = 2x^3 + 2x^2 - 7x +72 . . . . . . . . . . . . . . . . .(9)

Combining (3), (5), 8(0, and (9) we get

f(x) =4 . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . (10)