`0.3` is root of `x^(2)- 0.9 =0.`

Answer

To determine whether `0.3` is a root of the equation \( x^2 - 0.9 = 0 \), we will substitute `0.3` into the equation and see if it satisfies the equation.

### Step-by-Step Solution:

1. **Write down the equation**:
\[ x^2 - 0.9 = 0 \]

2. **Substitute `0.3` into the equation**:
\[ (0.3)^2 - 0.9 = 0 \]

3. **Calculate \( (0.3)^2 \)**:
\[ (0.3)^2 = 0.09 \]

4. **Substitute this value back into the equation**:
\[ 0.09 - 0.9 = 0 \]

5. **Perform the subtraction**:
\[ 0.09 - 0.9 = -0.81 \]

6. **Check if the result equals zero**:
\[ -0.81 \neq 0 \]

Since the left-hand side of the equation does not equal zero, we conclude that `0.3` is not a root of the equation \( x^2 - 0.9 = 0 \).

### Conclusion:
The statement that `0.3` is a root of the equation \( x^2 - 0.9 = 0 \) is **false**.