# Mistake in expression

While attempting to multiply the expression (2 - 5i)(5 + 2i) a student made a mistake.

(2 - 5i)(5 + 2i) = 10 + 4i - 25i - 10i2

= 10 + 4(-1) - 25(-1) - 10(1)

= 10 - 4 + 25 - 10

= 21

Complete the explanation and correct the error.

Hint: The student incorrectly defined i as being equal to ___ instead of ___. The student should have written the product as :

(2 - 5i)(5 + 2i) = 10 + 4i - 25i - 10i2

= 10 + 4(-1) - 25(-1) - 10(1)

= 10 - 4 + 25 - 10

= 21

Complete the explanation and correct the error.

Hint: The student incorrectly defined i as being equal to ___ instead of ___. The student should have written the product as :

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