How do you solve the quadratic 7k^2+7=-140 using any method?

1 Answer
Jim G.
Sep 4, 2016

k=+-isqrt21

Explanation:

Begin by isolating k^2

7k^2=-140-7=-147

rArrk^2=(-147)/7=-21

now take the color(blue)"square root" of both sides

rArrsqrt(k^2)=+-sqrt(-21)rArrk=+-sqrt(-21)

Now sqrt(-21)=sqrt(-1xx21)=sqrt(-1)xxsqrt21=i sqrt21

rArrk=+-isqrt21

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