Simplify (5 -3i)(2 + 5i)?

Question

Do it step by step :)

I got 10 + 19i - 15i^2 and I am stumped. You remove the ^2 but I have forgotten how and why

Answer 1

It just takes foiling-

(5*2)+(5*5i)+(-3i*2) +(-3i*5i)
(10)+(25i)+(-6i)+(-15*i^2)
i^2=-1
so...
25+19i

To those who have said that you can't simplify it past 10 + 19i - 15i^2, that isn't correct considering that since i is the square root of -1, i^2 is -1. That's why you can simplify -15i^2 to 15, thus making it 10+19i+15, or 25+19i

Answer 2

To do this you use the FOIL method. FOIL stands for firsts,outsides, insides, lasts.

Problem: (5-3i)(2+5i)

Firsts: (5)(2) = 10
Outsides: (5)(5i) = 25i
Insides: (-3i)(2) = -6i
Lasts: (-3i)(5i)=-15i^2

The next step is to add all these answers together and then simplify:

(10)+(25i)+(-6i)+(-15i^2)

Combine like terms: 25i and -6i = 19i
(10)+(19i)+(-15i^2)

You can't simplify more than what is above so the answer is:
10 + 19i - 15i^2

Hope this helped

Answer 3

(5-3i)(2+5i)=10+25i-6i-15i^2
=10+19i-15i^2
=10+19i-15x(-1)
=10+19i+15
=25+19i
therefore the answer is 25+19i
NOTE: i think that's how you do it. year 9 maths doesn teach imagery numbers and stuff like that

Answer 4

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

( 5 - 3i)(2 + 5i) = 10 - 6i + 25i - 15i² = 10 + 19i - 15i²

The answer is 10 + 19i - 15i²

- - - - - - - - - -s-

Answer 5

very easy. (5 + 5i) (4+i) = 20 + 5i +20i +5 i^2 since i^2 = -1 answer is 20 + 25i -5 so final answer is 15 +25i

Answer 6

(5-3i)(2+5i)=(5*2 + 5*5i - 3i*2 -3i*5i)=(10+25i-6i-15(i^2))= (10+19i-15(i^2) )