Answer:
10.5
Step-by-step explanation:
let the number be x, then subtract 20 is (x - 20) and square the result, that is
(x - 20)²
If I square the number, that is x² and subtract 20, then x² - 20
equate the two expressions
(x - 20)² = x² - 20 ← expand left side using FOIL
x² - 40x + 400 = x² - 20 ( subtract x² from both sides )
- 40x + 400 = - 20 ( subtract 400 from both sides )
- 40x = - 420 ( divide both sides by - 40 )
x = 10.5
The number is then 10.5
