To express $6i + i$ in the form $a + bi$, we start by combining the terms:

$6i + i = 7i$

Since there is no real part, we can write this as:

$0 + 7i$

Thus, in the form $a + bi$, the answer is:

$0 + 7i$

Would you like further details or have any questions?

Here are some related questions for practice:

1. Simplify $3i + 4i$ in the form $a + bi$.
2. Write $5 + 3i + 2i$ in the form $a + bi$.
3. Combine $4 + 2i + 3 - i$ into the form $a + bi$.
4. Express $-2i + 6i$ as $a + bi$.
5. Simplify $3i - 7i$ in the form $a + bi$.

Tip: When working with imaginary terms, remember to combine like terms (real with real, imaginary with imaginary) for clarity.