How do you solve #n^2-4=77#?

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Answer 1 · 2016-08-04T00:41:56

#n= 9#

#color(magenta)("Let's add 4 to both sides of the equation:"#

#n^2-cancel4=77#
#color (white)(aa) +cancel4 # #color(white)(a)+4 #

On the left side of the equation you're left with #n^2# since #(-4)+(4) = 0. # When 4 is added to 77 you obtain 81 on the right side:

#n^2 = 81#

Take the square root (since that is the inverse of squaring a number) on both sides of the equation to get n by itself:

#sqrt(n^2) = sqrt81#

Thus, #n = +- 9#

The plus or minus symbol means that the answer can be positive 9 or negative 9.