Find the positive root of the equation x 2 + x − 2 0 = 0 .
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I prefer this.
Completing square.
It is the easiest way for me to solve quadratic equation .
x^2 +x - 20
this equals,
x^2 + 5x - 4x - 20
or,
x(x + 5) - 4(x + 5)
i.e.
(x - 4)(x + 5)
So, either x = 4 or x = -5
Hence positive root equals 4 !!!!!!
x 2 + x − 2 0 = 0
( x − 4 ) ( x + 5 ) = 0
x − 4 = 0 , or x + 5 = 0 \
x = 4 , or x = − 5
But, we are looking for the positive root, so it is x = 4
One way to solve this is by factoring.
x 2 + x − 2 0 = 0
( x + 5 ) ( x − 4 ) = 0
x + 5 = 0
x = − 5
or
x − 4 = 0
x = 4
Therefore, the positive root is x = 4 .
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x 2 + x − 2 0 = 0
By factoring, we have
( x + 5 ) ( x − 4 ) = 0
x = − 5
x = 4
So the positive root is x = 4 .
Note: We can also use the quadratic formula.