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Use substitution to compose the two functions.

Given:
[tex]\[ P = 7q^2 + 9 \][/tex]
[tex]\[ q = 3r^3 \][/tex]

Find:
[tex]\[ P = \][/tex]


Sagot :

Certainly! We are given two functions:

1. [tex]\( P(q) = 7q^2 + 9 \)[/tex]
2. [tex]\( q(r) = 3r^3 \)[/tex]

We want to compose these two functions by substituting [tex]\( q(r) \)[/tex] into [tex]\( P(q) \)[/tex].

Step-by-step, here’s how we do this:

1. Start with the definition of [tex]\( P(q) \)[/tex]:

[tex]\[ P(q) = 7q^2 + 9 \][/tex]

2. Substitute [tex]\( q(r) = 3r^3 \)[/tex] into [tex]\( P(q) \)[/tex]. This means that everywhere there is a [tex]\( q \)[/tex] in the function [tex]\( P \)[/tex], we will replace it with [tex]\( 3r^3 \)[/tex]:

[tex]\[ P(r) = 7(3r^3)^2 + 9 \][/tex]

3. Now, simplify the expression inside the parentheses:

[tex]\[ (3r^3)^2 \][/tex]

This means raising [tex]\( 3r^3 \)[/tex] to the power of 2, which results in:

[tex]\[ (3r^3)^2 = 3^2 \cdot (r^3)^2 = 9r^6 \][/tex]

4. Substitute this back into the function for [tex]\( P \)[/tex]:

[tex]\[ P(r) = 7 \cdot 9r^6 + 9 \][/tex]

5. Simplify the constants by multiplying:

[tex]\[ P(r) = 63r^6 + 9 \][/tex]

Therefore, after performing the substitution and simplification, the composed function [tex]\( P \)[/tex] in terms of [tex]\( r \)[/tex] is:

[tex]\[ P = 63r^6 + 9 \][/tex]