Given that a is the longest side length in the triangle, which of the following inequalities would make the triangle above an obtuse triangle?
a. a2+b2< c2 b. a2+b2> c2 c. b2+c2< a2 d. b2+c2> c2

The equations presented in the choices above are all derived from the Pythagorean theorem. This states that the sum of the squares of the two shorter sides is equal to the square of the longest side which is also referred to as the hypotenuse. 

If the sum of the squares of the shorter sides is smaller compared to the square of the hypotenuse then, the triangle is OBTUSE. The answer therefore to this item is letter A. 

Ok here we go ..there are plenty of ways to solve such math problems but we will go for the smartest and easiest ..5x+2y=7  -2x+6y=9we rearrange them into the following ..by multiplying the 1st equation by 2 it becomes 10x + 4y = 14we rearrange it and so it becomes 10x = 14 - 4yas for the second equation we multiply it by 5 and rearrange it so it becomes as to the following ..-10x + 30y = 45rearranging so 10x = 30y -45now 10x equals both 14 - 4y and 30y -45so   14 - 4y = 30y -4531 = 26yy= 31/26 = 1.19 or around 1.2so by now we can calculate x easily as  -2x+6y=9so 2x = 6y -9 = 6 * 31/26 - 9 = -1.84  then x = - 0.92 or around -0.9best luck!