Combine Logs: Use the property of logarithms that allows us to combine the two log terms on the left side of the equation into a single log term by multiplication.log2(4x−3)+log2(3x+5)=log2((4x−3)(3x+5))
Exponential Form: Since the sum of the logs is equal to 3, we can rewrite the equation in exponential form to remove the logarithm.log2((4x−3)(3x+5))=3 is equivalent to 23=(4x−3)(3x+5)
Calculate Value: Calculate the value of 23.23=8
Set Product Equal: Set the product of the binomials equal to 8.(4x−3)(3x+5)=8
Expand Equation: Expand the left side of the equation using the distributive property (FOIL method). 4x(3x)+4x(5)−3(3x)−3(5)=812x2+20x−9x−15=8
Combine Like Terms: Combine like terms on the left side of the equation.12x2+20x−9x−15=812x2+11x−15=8
Set Equation to Zero: Subtract 8 from both sides to set the equation to zero.12x2+11x−15−8=012x2+11x−23=0
Quadratic Formula: Factor the quadratic equation or use the quadratic formula to find the values of x. This equation does not factor nicely, so we will use the quadratic formula.x=2a−b±b2−4acwhere a=12, b=11, and c=−23.
Calculate Solutions: Since the discriminant is positive, there are two real solutions. Calculate the solutions using the quadratic formula.x=2⋅12−11±1225x=24−11±35
Check Validity: Calculate the two possible values for x.x1=24−11+35x1=2424x1=1x2=24−11−35x2=24−46x2=−1223
Check Validity: Calculate the two possible values for x.x1=24−11+35x1=2424x1=1x2=24−11−35x2=24−46x2=12−23Check the solutions in the original equation to ensure they do not result in the logarithm of a negative number or zero, as the logarithm is not defined for these values.For x1=1:log2(4(1)−3)+log2(3(1)+5)=log2(4−3)+log2(3+5)=log2(1)+log2(8)=0+3=3This is valid.For x2=−1223:log2(4(−1223)−3)+log2(3(−1223)+5) involves the logarithm of negative numbers, which is not defined.This is not valid.Therefore, x2=−1223 is not a valid solution.
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