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Find the solution of the following initial value problem.

[tex]
g^{\prime}(x)=9 x\left(x^8-\frac{1}{9}\right) ; \quad g(1)=1
[/tex]

The solution is [tex]g(x)= \square[/tex]

Sagot :

To solve the given initial value problem, we need to follow these steps:

1. Identify the Differential Equation:

The differential equation given is:
[tex]\[ g'(x) = 9x \left(x^8 - \frac{1}{9}\right) \][/tex]

2. Integrate the Differential Equation:

We need to integrate [tex]\( g'(x) \)[/tex] with respect to [tex]\( x \)[/tex] to find [tex]\( g(x) \)[/tex]:
[tex]\[ g(x) = \int 9x \left(x^8 - \frac{1}{9}\right) \, dx \][/tex]

Breaking the integral into two parts, we get:
[tex]\[ g(x) = 9 \int x \cdot x^8 \, dx - 9 \int x \cdot \frac{1}{9} \, dx \][/tex]

Simplifying it further:
[tex]\[ g(x) = 9 \int x^9 \, dx - \int x \, dx \][/tex]

Computing these integrals:
[tex]\[ 9 \int x^9 \, dx = 9 \left(\frac{x^{10}}{10}\right) = 0.9 x^{10} \][/tex]
and
[tex]\[ \int x \, dx = \frac{x^2}{2} \][/tex]

Therefore:
[tex]\[ g(x) = 0.9 x^{10} - 0.5 x^2 + C \][/tex]
where [tex]\( C \)[/tex] is the constant of integration.

3. Apply the Initial Condition [tex]\( g(1) = 1 \)[/tex]:

To find [tex]\( C \)[/tex], we use the initial condition:
[tex]\[ g(1) = 0.9 (1)^{10} - 0.5 (1)^2 + C = 1 \][/tex]

Simplifying, we get:
[tex]\[ 0.9 - 0.5 + C = 1 \][/tex]
[tex]\[ 0.4 + C = 1 \][/tex]
[tex]\[ C = 1 - 0.4 = 0.6 \][/tex]

4. Write the Final Solution:

Substituting [tex]\( C = 0.6 \)[/tex] back into the expression for [tex]\( g(x) \)[/tex], we get:
[tex]\[ g(x) = 0.9 x^{10} - 0.5 x^2 + 0.6 \][/tex]

So, the solution to the initial value problem is:
[tex]\[ g(x) = 0.9 x^{10} - 0.5 x^2 + 0.6 \][/tex]