the square of a number plus the number is 72. find the number(S)

Step 1: Form an equation.

Let the number be S.

The square of S = S^2

So S2 + S = 72

S2+S-72 = 0

Step 2: Solve the equation.

S2 + S - 72 = 0

Look for factor whosr product is -72s2 and sum = S

Those factors are 9s and -8s

So

S2+ 9S - 8S -72 = 0

S(S + 9)- 8(S+9) = 0

(S+9) (S-8) = 0

S = -9 or 8

Hope this helps. You can ask any question if you are not satisfied.

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