question is : Simplify 2i3 + i2 - i
I think you mean i3 and i2 to be the complex number i raised to powers.
I'll use * to mean multiply. i squared is -1.
2*i*i*i + i*i - i = 2*(-1)*i + -1 - i = -2i -1 -i = -1-3i
If you just meant multiply, not exponent, then
2i3 + i2 -i = 6i + 2i -i = 7i
