If 2x=3+5i then find the value of 2x^3+2x^2-7x+72=?
If 2x=3+5i then find the value of 2x^3+2x^2-7x+72=?
To find the value of the expression 2x^3 + 2x^2 - 7x + 72, we first need to determine the value of x.
Given that 2x = 3 + 5i, we can solve for x by dividing both sides of the equation by 2:
2x/2 = (3 + 5i)/2
Simplifying, we get:
x = (3 + 5i)/2
To further simplify, we can multiply the numerator and denominator by the conjugate of 2, which is 2 - 0i:
x = (3 + 5i)(2 - 0i)/(2)(2 - 0i)
Expanding the numerator, we get:
x = (6 + 10i - 0i - 0i^2)/(4 - 0i)
Simplifying, we have:
x = (6 + 10i)/(4)
Dividing each term by 4:
x = 6/4 + 10i/4
Simplifying further, we get:
x = 3/2 + 5i/2
Now that we have the value of x, we can substitute it into the expression 2x^3 + 2x^2 - 7x + 72.
Substituting x = 3/2 + 5i/2, we have:
2(3/2 + 5i/2)^3 + 2(3/2 + 5i/2)^2 - 7(3/2 + 5i/2) + 72
Now, let's simplify each term step by step.
1. Simplifying (3/2 + 5i/2)^3:
To simplify this, we can use the binomial expansion formula.
(3/2 + 5i/2)^3 = (3/2)^3 + 3(3/2)^2(5i/2) + 3(3/2)(5i/2)^2 + (5i/2)^3
Expanding each term, we get:
(27/8) + (27/4)(5i/2) + (9/2)(25i^2/4) + (125i^3/8)
Simplifying i^2 and i^3:
(27/8) + (135i/8) - (225i^2/8) - (125i/8)
Since i^2 = -1 and i^3 = -i, we have:
(27/8) + (135i/8) - (225(-1)/8) - (125(-i)/8)
Simplifying further, we get:
(27/8) + (135i/8) + (225/8) + (125i/8)
Combining like terms, we have:
(252/8) + (260i/8)
Simplifying, we get:
(63/2) + (65i/2)
2. Simplifying (3/2 + 5i/2)^2:
To simplify this, we can use the binomial expansion formula
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