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5) For each, solve for [tex]\( x \)[/tex].

a) [tex]\( 7^x = 70 \)[/tex]

b) [tex]\( 2(5^x) - 4 = 76 \)[/tex]

Sagot :

Sure, let's solve each equation step by step.

### a) [tex]\( 7^x = 70 \)[/tex]

To solve for [tex]\( x \)[/tex], we can use logarithms.

1. Start with the given equation:
[tex]\[ 7^x = 70 \][/tex]

2. Take the natural logarithm (or common logarithm) of both sides to make use of the properties of logarithms:
[tex]\[ \log(7^x) = \log(70) \][/tex]

3. Use the logarithm power rule, [tex]\( \log(a^b) = b \log(a) \)[/tex], to bring the exponent down:
[tex]\[ x \log(7) = \log(70) \][/tex]

4. Solve for [tex]\( x \)[/tex] by dividing both sides of the equation by [tex]\( \log(7) \)[/tex]:
[tex]\[ x = \frac{\log(70)}{\log(7)} \][/tex]

Therefore, the solution to [tex]\( 7^x = 70 \)[/tex] is:
[tex]\[ x = \frac{\log(70)}{\log(7)} \][/tex]

### b) [tex]\( 2(5^x) - 4 = 76 \)[/tex]

To solve for [tex]\( x \)[/tex], follow these steps:

1. Start with the given equation:
[tex]\[ 2(5^x) - 4 = 76 \][/tex]

2. Add 4 to both sides to isolate the term with the exponent:
[tex]\[ 2(5^x) = 80 \][/tex]

3. Divide both sides by 2 to further isolate [tex]\( 5^x \)[/tex]:
[tex]\[ 5^x = 40 \][/tex]

4. Take the natural logarithm (or common logarithm) of both sides:
[tex]\[ \log(5^x) = \log(40) \][/tex]

5. Use the logarithm power rule, [tex]\( \log(a^b) = b \log(a) \)[/tex], to bring the exponent down:
[tex]\[ x \log(5) = \log(40) \][/tex]

6. Solve for [tex]\( x \)[/tex] by dividing both sides by [tex]\( \log(5) \)[/tex]:
[tex]\[ x = \frac{\log(40)}{\log(5)} \][/tex]

Therefore, the solution to [tex]\( 2(5^x) - 4 = 76 \)[/tex] is:
[tex]\[ x = \frac{\log(40)}{\log(5)} \][/tex]

These are the solutions for the given equations.