Question
Simplify: Write answers in the form of a + bi, where a and b are real numbers.
a. (1-2i)(1+3i)
b. (3-5i)(8-2i)
a. (1-2i)(1+3i)
b. (3-5i)(8-2i)
Answers
bobpursley
Use FOIL to multiply them out.
Breanna
IS this correct, i notice that i^2 = -1 what does this mean?
(1-2i)(1+3i)
=1+3i-2i-6i^2
=1+ i-6i^2
= 1+i-6i
(1-2i)(1+3i)
=1+3i-2i-6i^2
=1+ i-6i^2
= 1+i-6i
bobpursley
no, 6i^2 is 6*(-1)
so the last term is +6 and the final answer is
7+i
so the last term is +6 and the final answer is
7+i
Breanna
So did I do any of this correct? What do I need to fix?
MathMate
You have basically done it correctly, but omitted to change the sign of the last term because i<sup>2</sup>=-1
(1-2i)(1+3i)
=1+3i-2i-6i^2
=1+ i-6i^2
= 1+i <b>+</b>6i
(1-2i)(1+3i)
=1+3i-2i-6i^2
=1+ i-6i^2
= 1+i <b>+</b>6i
MathMate
Oops, it should read:
(1-2i)(1+3i)
=1+3i-2i-6i^2
=1+ i-6i^2
= 1+i <b>+</b>6
=<b>7+i</b>
(1-2i)(1+3i)
=1+3i-2i-6i^2
=1+ i-6i^2
= 1+i <b>+</b>6
=<b>7+i</b>
Mnahil
Give me answers of 2.6 of 9 class