Question
Solve the equation
x=56
Evaluate
log5(2x2−8x×7)=2log5(x)
Find the domain
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Evaluate
{2x2−8x×7>0x>0
Calculate
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Evaluate
2x2−8x×7>0
Multiply the terms
2x2−56x>0
Evaluate
x2−28x>0
Add the same value to both sides
x2−28x+196>196
Evaluate
(x−14)2>196
Take the 2-th root on both sides of the inequality
(x−14)2>196
Calculate
∣x−14∣>14
Separate the inequality into 2 possible cases
x−14>14x−14<−14
Calculate
x>28x−14<−14
Cancel equal terms on both sides of the expression
x>28x<0
Find the union
x∈(−∞,0)∪(28,+∞)
{x∈(−∞,0)∪(28,+∞)x>0
Find the intersection
x>28
log5(2x2−8x×7)=2log5(x),x>28
Multiply the terms
log5(2x2−56x)=2log5(x)
Move the expression to the left side
log5(2x2−56x)−2log5(x)=0
Add the terms
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Evaluate
log5(2x2−56x)−2log5(x)
Use the logarithm base change rule
log5(2x2−56x)−log5(x2)
Use logax−logay=logayx to transform the expression
log5(x22x2−56x)
Divide the terms
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Evaluate
x22x2−56x
Factor
x2x(2x−56)
Reduce the fraction
x2x−56
log5(x2x−56)
log5(x2x−56)=0
Convert the logarithm into exponential form using the fact that logax=b is equal to x=ab
x2x−56=50
Evaluate the power
x2x−56=1
Cross multiply
2x−56=x
Move the variable to the left side
2x−56−x=0
Subtract the terms
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Evaluate
2x−x
Collect like terms by calculating the sum or difference of their coefficients
(2−1)x
Subtract the numbers
x
x−56=0
Move the constant to the right side
x=0+56
Removing 0 doesn't change the value,so remove it from the expression
x=56
Check if the solution is in the defined range
x=56,x>28
Solution
x=56
Show Solution
