tolong no 4..............

-MATEMATIKA-
Bab: Logaritma

[tex]1. \: 5log_{2x} = 5log_{20} \\ \: 2x = 20 \\ \: x = 10[/tex]

[tex]2. \:3 log_{(3x + 1)} =3 log_{25} \\ \: 3x + 1 = 25 \\ \: 3x = 24 \\ \: x = 8[/tex]

[tex]3. \: xlog_{(2x + 3)} = xlog_{(x + 9)} \\ \: 2x + 3 = x + 9 \\ \: x = 6[/tex]

[tex]4. \: 4log_{(5x + 4)} = 3 \\ \: 4log_{(5x + 4)} = 4 log_{64} \\ \: 5x + 4 = 64 \\ \: x = 12[/tex]

[tex]5. \:2 log_{ ({2x}^{2} + 15) } = 2log_{ ({x}^{2} + 8x) } \\ \: {2x}^{2} + 15 = {x}^{2} + 8x \\ \: {2x}^{2} - {x}^{2} - 8x + 15 = 0 \\ \: {x}^{2} - 8x + 15 = 0 \\ \: (x - 5)(x - 3) = 0 \\ \: x = 5 \: atau \: x = 3[/tex]

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