Bonjours je ne comprends pas cet exercice en anglais IN ENGLISH
▶p. 381
The lengths of the sides of a right-angled triangle are
given by the expressions x - 1, 4x and 5.x - 9, as shown
in the diagram.
5x-9
4.x
x-1
a. Find the value of x.
b. Verify, with this value of x, that the lengths of the sides
of the triangle above form a Pythagorean triple.