Answer:
see explanation
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides , that is
AB² + BC² = AC² ( substitute values )
x² + (x + 7)² = 17² ← expand factor on left side using FOIL
x² + x² + 14x + 49 = 289
2x² + 14x + 49 = 289 ( subtract 289 from both sides )
2x² + 14x - 240 = 0 ( divide through by 2 )
x² + 7x - 120 = 0 ← as required
