Answer:
x = 16 inches
Step-by-step explanation:
Let the length of a rectangular screen is x inches.
Then from the statement of the question width of the screen will be (x -4) inches.
Now we apply Pythagoras theorem
x²+(x - 4)² = 20²
x² + x² + 16 - 8x = 400
2x²- 8x + 16 - 400 = 0
2x² - 8x - 384 = 0
x² - 4x - 192 = 0
From quadratic formula
[tex]x=\frac{4\pm \sqrt{16+4\times 192}}{2}=\frac{4\pm \sqrt{16+768}}{2}=\frac{4\pm \sqrt{784}}{2}=\frac{4\pm 28}{2}=\frac{32}{2}and -\frac{24}{2}[/tex]
Since length of screen can not be in negative notation.
Therefore x = 16 inches is the answer.
