- A25 and 29
- B30 and 34
- C35 and 39
- D40 and 44
View written solutionFree
Correct answer: C
Step-by-step Solution:
1. Understand the definitions of the sets A, B, and C.
Let a complex number be represented as z = x + iy, where x and y are real numbers.
-
Set A: The imaginary part of
zisy. So, this condition is . Geometrically, this represents the upper half-plane including the liney = 1. -
Set B: This can be written as
|z - (2 + i)| = 3. This represents all pointszin the complex plane whose distance from the point(2 + i)is 3. Geometrically, this is a circle with center and radiusr = 3. The equation in Cartesian coordinates is . -
Set C: Let's compute
(1 - i)z: The real part isRe((1 - i)z) = x + y. So, the condition is . Geometrically, this is a straight line.
2. Analyze the expression to be evaluated.
The expression is .
Let's express this in terms of x and y:
$z + 1 - i = (x + 1) + i(y - 1)$
$z - 5 - i = (x - 5) + i(y - 1)$
Now, sum these two parts:
Let's complete the square for the terms involving x:
3. Use the condition from Set B.
Any point z in the intersection must belong to set B. The condition for z to be in B is .
Substituting this into our simplified expression for E:
$E = 2(9) + 18 = 18 + 18 = 36$
This means that for any point z on the circle defined by set B, the value of the expression is exactly 36.
4. Verify that the intersection is not empty.
We need to ensure there exists at least one point z that satisfies the conditions for all three sets. We need to find if the line (from C) intersects the circle (from B) in the region (from A).
-
Intersection of B and C: The distance
dfrom the center of the circle(2, 1)to the line is: Since , . The radius of the circle isr = 3. Sinced < r, the line intersects the circle at two distinct points. -
Checking condition A: We need to see if at least one of these intersection points has a y-coordinate greater than or equal to 1. The center of the circle is at
y=1. The line passes through the point . Since , and the line has a slope of -1, one part of the line segment chord inside the circle will be abovey=1and the other below. Thus, one of the intersection points will havey > 1. Therefore, the intersection is non-empty.
5. Final Conclusion.
Since a point z exists in , and for any such point (as it must be in B), the expression evaluates to 36. We need to find which of the given intervals contains the value 36.
- A: 25 and 29 (25 < 36 < 29 is false)
- B: 30 and 34 (30 < 36 < 34 is false)
- C: 35 and 39 (35 < 36 < 39 is true)
- D: 40 and 44 (40 < 36 < 44 is false)
The value 36 lies between 35 and 39.
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