Answer: x = 3.95
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Explanation:
Use the pythagorean theorem to tie together the three sides of the right triangle.
[tex]a = x-3 = \text{horizontal leg}\\b = x+5 = \text{vertical leg}\\c = 9 = \text{hypotenuse}[/tex]
[tex]a^2 + b^2 = c^2\\(x-3)^2 + (x+5)^2 = 9^2\\x^2-6x+9 + x^2+10x+25 = 81\\2x^2+4x+34 = 81\\2x^2+4x+34-81=0\\2x^2+4x-47=0\\[/tex]
From here, we use the quadratic formula to solve for x.
[tex]x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}\\\\x = \frac{-(4)\pm\sqrt{(4)^2-4(2)(-47)}}{2(2)}\\\\x = \frac{-4\pm\sqrt{392}}{4}\\\\x \approx \frac{-4\pm19.79898987}{4}\\\\x \approx \frac{-4+19.79898987}{4} \ \text{ or } \ x \approx \frac{-4-19.79898987}{4}\\\\x \approx \frac{15.79898987}{4} \ \text{ or } \ x \approx \frac{-23.79898987}{4}\\\\x \approx 3.94974747 \ \text{ or } \ x \approx -5.94974745\\\\[/tex]
We'll ignore the negative x value because it makes the sides x+5 and x-3 to be negative numbers. Negative side lengths make no sense.
The only practical solution is roughly x = 3.94974747; rounding to 3 sig figs leads to the final answer of x = 3.95
In this case, 3 sig figs means that we're rounding to 2 decimal places.
