express (7+5i) (7-5i) in the form of a+ ib
Answers
Answered by
0
Step-by-step explanation:
Answer
Shwetank Mauria
Feb 12, 2017
(
7
+
5
i
)
(
7
−
5
i
)
=
74
+
i
0
Explanation:
Using the identity
(
a
+
b
)
(
a
−
b
)
=
a
2
−
b
2
(
7
+
5
i
)
(
7
−
5
i
)
=
7
2
−
(
5
i
)
2
=
49
−
25
i
2
- but
i
2
=
−
1
Hence this is
49
−
25
×
(
−
1
)
=
49
+
25
=
74
and in standard form, this can be written as
74
+
i
0
Answered by
0
74+0i
Step-by-step explanation:
We know that,
(a+b) (a-b) = a²- b²
(7 + 5i) (7-5i)
=(7)² - (5i)²
=49 - 25i²
= 49 + 25 {i² = - i}
= 74
= 74 +0i.....
Similar questions