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(ii) Fiad \( p \) and 9 given that \( 2 p+3 i q+\frac{1}{1+i}-(2+i)^{2} \), (iii) Solve the inequatity \( |x+2| \geqslant 3 \).

Ask by Savage Goodwin. in Zambia
Mar 13,2025

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Answer

**(ii)** The values are \( p = \frac{5}{4} \) and \( q = \frac{3}{2} \). **(iii)** The solution to the inequality \( |x+2| \geqslant 3 \) is \( x \leqslant -5 \) or \( x \geqslant 1 \).

Solution

**(ii)** We are given the equation \[ 2p+3iq+\frac{1}{1+i}-(2+i)^2=0. \] Assuming \(p\) and \(q\) are real numbers, we begin by simplifying the complex fractions and powers. 1. Compute \((2+i)^2\): \[ (2+i)^2 = 2^2+2\cdot2\cdot i+i^2 = 4+4i-1=3+4i. \] 2. Simplify \(\frac{1}{1+i}\) by multiplying the numerator and denominator by the conjugate \(1-i\): \[ \frac{1}{1+i}=\frac{1}{1+i}\cdot\frac{1-i}{1-i}=\frac{1-i}{(1+i)(1-i)}=\frac{1-i}{1^2-i^2}=\frac{1-i}{1-(-1)}=\frac{1-i}{2}=\frac{1}{2}-\frac{i}{2}. \] 3. Substitute these results into the original equation: \[ 2p+3iq+\left(\frac{1}{2}-\frac{i}{2}\right)-(3+4i)=0. \] Group the real and imaginary parts: - **Real part:** \[ 2p+\frac{1}{2}-3 =2p-\frac{5}{2}. \] - **Imaginary part:** \[ 3iq-\frac{i}{2}-4i=i\left(3q-\frac{1}{2}-4\right)=i\left(3q-\frac{9}{2}\right). \] 4. For the complex equation to be zero, both the real part and the imaginary part must vanish: - **Real part:** \[ 2p-\frac{5}{2}=0 \quad\Longrightarrow\quad 2p=\frac{5}{2}\quad\Longrightarrow\quad p=\frac{5}{4}. \] - **Imaginary part:** \[ 3q-\frac{9}{2}=0 \quad\Longrightarrow\quad 3q=\frac{9}{2}\quad\Longrightarrow\quad q=\frac{9}{6}=\frac{3}{2}. \] Thus, \[ \boxed{p=\frac{5}{4},\quad q=\frac{3}{2}}. \] --- **(iii)** We need to solve the inequality \[ |x+2|\geqslant 3. \] The absolute value inequality \( |x+2|\geqslant 3 \) means that the expression inside the absolute value is either at least 3 or at most \(-3\). This gives us two cases: 1. \( x+2\geqslant 3 \) \[ x+2\geqslant 3\quad\Longrightarrow\quad x\geqslant 1. \] 2. \( x+2\leqslant -3 \) \[ x+2\leqslant -3\quad\Longrightarrow\quad x\leqslant -5. \] Hence, the solution is \[ \boxed{x\leqslant -5\quad\text{or}\quad x\geqslant 1}. \]

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Bonus Knowledge

To tackle the expression \( 2 p + 3 i q + \frac{1}{1+i} - (2+i)^{2} \), first, we can simplify it. The term \( \frac{1}{1+i} \) simplifies to \( \frac{1 - i}{2} \) and \( (2+i)^{2} \) expands to \( 4 + 4i - 1 = 3 + 4i \). Thus, combine all components carefully to find \( p \) and \( q \). As for the inequality \( |x+2| \geqslant 3 \), we can rewrite this as two separate inequalities: \( x + 2 \geqslant 3 \) or \( x + 2 \leqslant -3 \). Solving these gives \( x \geqslant 1 \) or \( x \leqslant -5 \). Therefore, the solution set consists of intervals \( (-\infty, -5] \) and \( [1, \infty) \).

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