Pearson Algebra 2 Common Core, 2011
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Pearson Algebra 2 Common Core, 2011 View details
6. Natural Logarithms
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Exercise 26 Page 481

A natural logarithm is a logarithm with base e.

± 0.908

Practice makes perfect
To solve the given logarithmic equation, we will start by applying inverse operations and the Properties of Equality to isolate the term with the logarithm. 2 ln 2x^2 = 1 ⇔ ln 2x^2 = 1/2 Now that we have isolated the term with the exponent, we will recall the definition of a logarithm. log_b x=y ⇔ x= b^yThis tells us how we can rewrite the logarithm equivalent to y as an exponential equation. The argument x is equal to b raised to the power of y. The base of a natural logarithm is e, so ln x = log_e x. Let's rewrite the given equation in exponential form. ln ( 2x^2)=1/2 ⇔ 2x^2= e^()darkviolet 12 Now, we can solve the equation for x.
2x^2=e^(12)
x^2=e^(12)/2
x= ± sqrt(e^(12)/2)
The exact solutions are x=sqrt(e^(12)/2) and x = - sqrt(e^(12)/2). We can also write them in decimal form using a calculator. sqrt(e^(12)/2) &≈ 0.908 - sqrt(e^(12)/2) &≈ - 0.908 Finally, we will check our answers by substituting 0.908 and - 0.908 for x in the given equation. Let's start with substituting 0.908.
2 ln 2x^2=1
2 ln(2 ( 0.908)^2)? =1
Evaluate left-hand side
2 ln 2(0.824)? =1
2 ln 1.648 ? =1

Calculate logarithm

2 (0.499) ? =1
0.998=1 ✓
Since substituting 0.908 for x produced a true statement, our answer is correct. Now, let's substitute - 0.908 fo x in the given equation.
2 ln 2x^2=1
2 ln(2 ( - 0.908)^2)? =1
Evaluate left-hand side
2 ln(2 (0.908)^2)? =1
2 ln 2(0.824)? =1
2 ln 1.648 ? =1

Calculate logarithm

2 (0.499) ? =1
0.998=1 ✓
Since substituting - 0.908 for x also produced a true statement, our answer is correct, too.