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sdas [7]
3 years ago
7

A student multiplies (4+5i) (3-2i) incorrectly and obtains 12-10i what is the students mistakes

Mathematics
1 answer:
Rufina [12.5K]3 years ago
4 0

Answer:

1. In the multiplication of the imaginary parts, the student forgot to square of i. OR

2. The student has only multiplied the real parts and the imaginary parts.

Correct value =22+7i.

Step-by-step explanation:

The given expression is

(4+5i)(3-2i)

A student multiplies (4+5i) (3-2i) incorrectly and obtains 12-10i.

Student's mistake can be either 1 or second:

1. In the multiplication of the imaginary parts, the student forgot to square of i.

2. The student has only multiplied the real parts and the imaginary parts.

(4+5i)(3-2i)=4\times 3+5\times (-2)i=12-10i

Which is not correct. The correct steps are shown below.

Using distributive property, we get

4(3-2i)+5i(3-2i)

4(3)+4(-2i)+5i(3)+5i(-2i)

12-8i+15i-10i^2

12+7i-10(-1)       [\because i^2=-1]

12+7i+10

22+7i

Therefore, the correct value of (4+5i)(3-2i) is 22+7i.

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