### Instruction: Simplify $2a(2a^2 + a) - a^2$.### Response: Ok, let's first expand the first term.
The first term is $2a(2a^2 + a)$.
Right. So, if we use the distributive property, we get $4a^3 + 2a^2$.
Now let's subtract $a^2$ from that.
That would be $4a^3 + a^2$.
And that's the same as $a^2(4a + 1)$.