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In a right triangle, the legs [tex]l_1[/tex] and [tex]l_2[/tex] are related with the hypotenuse [tex]h[/tex] by the Pythagorean Theorem, given below:
[tex]h^2 = l_1^2 + l_2^2[/tex]
In this problem:
Applying the Pythagorean Theorem:
[tex]h^2 = l_1^2 + l_2^2[/tex]
[tex]9^2 + x^2 = (x + 1)^2[/tex]
[tex]81 + x^2 = x^2 + 2x + 1[/tex]
[tex]2x + 1 = 81[/tex]
[tex]2x = 80[/tex]
[tex]x = \frac{80}{2}[/tex]
[tex]x = 40[/tex]
A similar problem is given at https://brainly.com/question/21691542