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In the figure below, find the value of 'x'.

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#### Solution

In the right-angled triangle EDF, ∠D = 90°. Hence, side EF is the hypotenuse.

According to Pythagoras' theorem,

l(EF)^{2} = l(ED)^{2} + l(DF)^{2}

⇒ (17)^{2} = (x)^{2} + (8)^{2}

⇒ 289 = x^{2} + 64

⇒ x^{2} = 289 − 64

⇒ x^{2} = 225

⇒ x^{2} = (15)^{2}

⇒ x = 15

∴ The value of x is 15.

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