Determinan 76. Determinan dari matriks $A=\left(\begin{matrix}\sqrt{2}&\sqrt{8}\\\frac{1}{2}&\frac{1}{2}\end{matrix}\right)$ adalah …. A. $-\sqrt{2}$ B. $-\frac{1}{2}\sqrt{2}$ C. $\frac{1}{2}\sqrt{2}$ D. $\sqrt{2}$ E. $2\sqrt{2}$ Jawaban: B $|A|=\left(\sqrt{2}\times\frac{1}{2}\right)-\left(\sqrt{8}\times\frac{1}{2}\right)$ , ingat $\sqrt{8}=2\sqrt{2}$ $|A|=\frac{1}{2}\sqrt(2)-\frac{1}{2}\times 2\sqrt{2}$ $|A|=\frac{1}{2}\sqrt(2)-\frac{2}{2} \sqrt{2}$ $|A|=-\frac{1}{2} \sqrt{2}$ 77. Diketahui $\left|\begin{matrix}a&2\\1&5\end{matrix}\right|=4a+2$. Nilai $a\sqrt{a}=$... A. 1 B. 2 C. $2\sqrt{2}$ D. 8 E. 12 Pembahasan: D Ingat; $\left|\begin{matrix}a&a\\1&5\end{matrix}\right|=(a\times 5)-(2\times 1)=5a-2$, sehingga $5a-2=4a+2$ $5a-2+2-4a=4a-4a+2+2$
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