How do you solve the quadratic $7x^2+5=-137$ using any method?

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Answer 1 · 2016-12-29T10:40:23

There are no real solutions. But you can solve this using complex numbers. Then, the solutions (both imaginary) are:

$x_1 = + sqrt {142/7} cdot i and x_2 = - sqrt {142/7} cdot i$

You can probe there are no solutions in $RR$ clearing the $x$ as follows:

$7 x^2 + 5 = - 137 color(white) "." rArr color(white) "." 7 x^2 = - 137 - 5 = - 142$ ,

then

$7 x^2 = - 142 color(white) "." rArr color(white) "." x^2 = - 142/7 color(white) "." rArr color(white) "." x = +- sqrt {- 142/7} !in RR$ .

However, if we still want to give an answer, we can use complex numbers using the definition of the imaginary number $i$ :

Since $i = sqrt {- 1}$ we can write the solutions of the quadratic equation of the form:

$x = +- sqrt {- 142/7} = +- sqrt {142/7} cdot sqrt {- 1} = +- sqrt {142/7} cdot i in CC$ .

How do you solve the quadratic 7x^2+5=-1377x^2+5=-137 using any method?