How do you solve x^2 - 8x - 20 = 0 by completing the square?
2 Answers
Explanation:
In addition to completing the square we can use the difference of squares identity:
a^2-b^2 = (a-b)(a+b)
with
0 = x^2-8x-20
=(x-4)^2-4^2-20
=(x-4)^2-16-20
=(x-4)^2-36
=(x-4)^2-6^2
=((x-4)-6)((x-4)+6)
=(x-10)(x+2)
So
Explanation:
This can be written as
Let
Add 16 to both sides:
We know that
Find the square root of both the sides:
When,
Add 4 to both sides:
When,
Add 4 to both sides: