Question 948046
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Tutor @CubeyThePenguin has supplied another careless response with a wrong answer....<br>
i^15 = (i^12)(i^3) = (1)(-i) = -i<br>
i^7 = (i^4)(i^3) = (1)(-i) = -i<br>
So<br>
2i^15 - i^7 = 2(-i)-(-i) = -2i+i = -i<br>