Find all the real square roots of 400. 20 -20 and 20 -40 -40 and 40

  The square roots of 400 are 20 and -20.

Step-by-step explanation:

You can try the offered answers to see if they square to give 400:

  (-40)² = 1600 . . . . -40 is not a square root of 400

  (-20)² = 400 . . . . -20 is a square root of 400

  20² = 400 . . . . . 20 is a square root of 400

  40² = 1600 . . . . 40 is not a square root of 400

The second degree equation ...

  x² = 400

will have exactly two solutions, as required by the fundamental theorem of algebra. Those solutions are both given above. There are no other square roots of 400, real or complex.

yes

step-by-step explanation: