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Vir watter waarde(s) van \( k \) sal die wortels van die vergelyking \( x^{2}-5 x-k=0 \) : \( \begin{array}{ll}\text { (a) gelyk wees? (b) reëel wees? } & \text { (c) nie-reëel wees? } \\ \text { Vir watter waarde(s) van } k \text { sal die wortels van die vergelyking } k x^{2}+2 k x=-3 \\ \text { gelyk wees as } k \neq 0\end{array} \)

Ask by Fitzgerald Boyd. in South Africa
Mar 12,2025

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Answer

For the equation \( x^{2} - 5x - k = 0 \): - (a) The roots are equal when \( k = -\frac{25}{4} \). - (b) The roots are real when \( k \geq -\frac{25}{4} \). - (c) The roots are not real when \( k < -\frac{25}{4} \). For the equation \( kx^{2} + 2kx = -3 \) with \( k \neq 0 \), the roots are equal when \( k = 3 \).

Solution

LaTeX \[ \textbf{Opgave 1: } x^2-5x-k=0. \] 1. Die diskriminant vir 'n kwadratiese vergelyking \( ax^2+bx+c=0 \) is: \[ \Delta = b^2-4ac. \] Hier, \( a=1 \), \( b=-5 \) en \( c=-k \). Dus is \[ \Delta = (-5)^2 - 4\cdot1\cdot(-k)=25+4k. \] 2. (a) Wolkens (gelyke wortels) beteken dat \(\Delta=0\). Ons los op: \[ 25+4k=0 \quad \Rightarrow \quad 4k=-25 \quad \Rightarrow \quad k=-\frac{25}{4}. \] 3. (b) Daar is reële wortels as \(\Delta\ge 0\): \[ 25+4k\ge 0 \quad \Rightarrow \quad 4k\ge -25 \quad \Rightarrow \quad k\ge -\frac{25}{4}. \] 4. (c) Daar is nie-reële wortels as \(\Delta<0\): \[ 25+4k<0 \quad \Rightarrow \quad 4k< -25 \quad \Rightarrow \quad k< -\frac{25}{4}. \] --- LaTeX \[ \textbf{Opgave 2: } kx^2+2kx=-3 \quad \text{met } k\neq 0. \] 1. Skryf die vergelyking in standaard vorm: \[ kx^2 +2kx +3=0. \] 2. Vir die kwadratiese vergelyking \(ax^2+bx+c=0\) waar \( a=k \), \( b=2k \) en \( c=3 \) is, bereken die diskriminant: \[ \Delta = (2k)^2-4\cdot k\cdot 3 = 4k^2-12k = 4k(k-3). \] 3. Vir gelyke wortels benodig ons \(\Delta=0\): \[ 4k(k-3)=0. \] Omdat \( k\neq 0 \) moet die oplossing wees: \[ k-3=0 \quad \Rightarrow \quad k=3. \]

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The Deep Dive

Vir die vergelyking \( x^{2}-5x-k=0 \) kan ons die diskriminant gebruik, wat gegee word deur \( D = b^2 - 4ac \). Hier is \( a = 1 \), \( b = -5 \), en \( c = -k \). (a) Die wortels is gelyk wanneer \( D = 0 \), wat lei tot \( (-5)^2 - 4(1)(-k) = 0 \). Dit gee \( 25 + 4k = 0 \), wat lei tot \( k = -\frac{25}{4} \). (b) Die wortels is reëel wanneer \( D \geq 0 \), wat lei tot \( 25 + 4k \geq 0 \). Dit gee \( k \geq -\frac{25}{4} \). (c) Die wortels is nie-reëel wanneer \( D < 0 \), wat lei tot \( 25 + 4k < 0 \). Dit gee \( k < -\frac{25}{4} \). Vir die vergelyking \( kx^{2} + 2kx = -3 \) kan ons dit herskryf as \( kx^{2} + 2kx + 3 = 0 \). Die wortels is gelyk wanneer die diskriminant \( D = 0 \), so \( (2k)^2 - 4k(3) = 0 \). Dit gee \( 4k^2 - 12k = 0 \), wat lei tot \( k(4k - 12) = 0 \), dit beteken dat \( k = 0 \) of \( k = 3 \). Aangesien ons \( k \neq 0 \) aanvaar, is die oplossing \( k = 3 \) vir gelyke wortels.

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