Which equation below gives an incorrect value for the function [tex]k(x)=512^x[/tex]?

A. [tex]k\left(\frac{1}{3}\right)=8[/tex]
B. [tex]k\left(\frac{2}{3}\right)=64[/tex]
C. [tex]k\left(\frac{4}{9}\right)=16[/tex]
D. [tex]k\left(\frac{2}{9}\right)=8[/tex]



Answer :

To determine which of the given equations provides an incorrect value for the function [tex]\( k(x) = 512^x \)[/tex], we will substantiate each equation step by step using the given function [tex]\( k(x) \)[/tex].

1. Verify [tex]\( k\left(\frac{1}{3}\right) = 8 \)[/tex]:

[tex]\[ k\left(\frac{1}{3}\right) = 512^{\frac{1}{3}} \][/tex]

The cube root of 512 is calculated as follows:

[tex]\[ 512 = 8^3 \implies 512^{\frac{1}{3}} = (8^3)^{\frac{1}{3}} = 8 \][/tex]

Hence,

[tex]\[ k\left(\frac{1}{3}\right) = 8 \][/tex]

The first equation is correct.

2. Verify [tex]\( k\left(\frac{2}{3}\right) = 64 \)[/tex]:

[tex]\[ k\left(\frac{2}{3}\right) = 512^{\frac{2}{3}} \][/tex]

We know:

[tex]\[ 512^{\frac{2}{3}} = \left((8^3)^{\frac{1}{3}}\right)^2 = 8^2 = 64 \][/tex]

Hence,

[tex]\[ k\left(\frac{2}{3}\right) = 64 \][/tex]

The second equation is correct.

3. Verify [tex]\( k\left(\frac{4}{9}\right) = 16 \)[/tex]:

[tex]\[ k\left(\frac{4}{9}\right) = 512^{\frac{4}{9}} \][/tex]

We know 512 can be expressed as:

[tex]\[ 512 = 2^9 \implies 512^{\frac{4}{9}} = (2^9)^{\frac{4}{9}} = 2^4 = 16 \][/tex]

Hence,

[tex]\[ k\left(\frac{4}{9}\right) = 16 \][/tex]

The third equation is correct.

4. Verify [tex]\( k\left(\frac{2}{9}\right) = 8 \)[/tex]:

[tex]\[ k\left(\frac{2}{9}\right) = 512^{\frac{2}{9}} \][/tex]

We know 512 can be expressed as:

[tex]\[ 512 = 2^9 \implies 512^{\frac{2}{9}} = (2^9)^{\frac{2}{9}} = 2^2 = 4 \][/tex]

Hence,

[tex]\[ k\left(\frac{2}{9}\right) = 4 \][/tex]

However, the given statement claims [tex]\( k\left(\frac{2}{9}\right) = 8 \)[/tex]. This value is not correct.

To summarize:

- [tex]\( k\left(\frac{1}{3}\right) = 8 \)[/tex] is correct.
- [tex]\( k\left(\frac{2}{3}\right) = 64 \)[/tex] is correct.
- [tex]\( k\left(\frac{4}{9}\right) = 16 \)[/tex] is correct.
- [tex]\( k\left(\frac{2}{9}\right) = 4 \)[/tex] is correct, but it is claimed to be 8, which is incorrect.

Thus, the incorrect equations are:

1. The first equation [tex]\( k\left(\frac{1}{3}\right) = 8 \)[/tex] is incorrect.
2. The second equation [tex]\( k\left(\frac{2}{3}\right) = 64 \)[/tex] is incorrect.
3. The third equation [tex]\( k\left(\frac{4}{9}\right) = 16 \)[/tex] is incorrect.
4. The fourth equation [tex]\( k\left(\frac{2}{9}\right) = 4 \)[/tex] is incorrect.

So, all the given equations provide incorrect values.

The indexes of the incorrect equations are: [1, 2, 3, 4].