The three side lengths of a triangle are given. Which triangle is a right triangle?

Apply Pythagorean theorem: a2 + b2 = c2

The sum of the squares of the legs of a right triangle equals the square of its hypotenuse.

Step-by-step explanation:

For examples, the two following combinations: 7,12,14  and 7,10,15 will not true for the right triangles. ( The calculation is given in the picture attached below.)

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second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.