Log2(8x-3)-log2 5 =1

Лебедев Дмитрий Сергеевич

Учитель математики

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To solve the equation log2(8x3)log25=1log base 2 of open paren 8 x minus 3 close paren minus log base 2 of 5 equals 1, we will use the properties of logarithms and follow a step-by-step algebraic approach. 1. Identify Constraints (Domain) The argument of a logarithm must be strictly greater than zero. Therefore: 8x3>08 x minus 3 is greater than 0 8x>38 x is greater than 3 x>38 (or x>0.375)x is greater than three-eighths (or x is greater than 0.375 close paren 2. Apply Logarithmic Properties Using the quotient rule, logb(a)logb(c)=logb(ac)log base b of a minus log base b of c equals log base b of open paren a over c end-fraction close paren , we can combine the left side of the equation: log2(8x35)=1log base 2 of open paren the fraction with numerator 8 x minus 3 and denominator 5 end-fraction close paren equals 1 3. Convert to Exponential Form By definition, if logb(y)=xlog base b of y equals x, then bx=yb to the x-th power equals y. Applying this here: 8x35=21the fraction with numerator 8 x minus 3 and denominator 5 end-fraction equals 2 to the first power 8x35=2the fraction with numerator 8 x minus 3 and denominator 5 end-fraction equals 2 4. Solve for xx Now, we perform basic algebraic operations to isolate xx:

  • Multiply both sides by 5:
    8x3=258 x minus 3 equals 2 center dot 5 8x3=108 x minus 3 equals 10 Add 3 to both sides:
    8x=138 x equals 13 Divide by 8:
    x=138x equals thirteen-eighths x=1.625x equals 1.625

5. Verify the Result Since 1.625>0.3751.625 is greater than 0.375, the solution falls within the defined domain. We can also plug it back into the original equation:

  1. 8(1.625)3=133=108 open paren 1.625 close paren minus 3 equals 13 minus 3 equals 10 log2(10)log2(5)=log2(10/5)=log2(2)log base 2 of 10 minus log base 2 of 5 equals log base 2 of open paren 10 / 5 close paren equals log base 2 of 2 log2(2)=1log base 2 of 2 equals 1

Final Answer: x=138 or 1.625x equals thirteen-eighths or 1.625 Would you like me to solve another logarithmic equation or demonstrate how to apply these properties to a different base?

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