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in a triangle ABC, AB=x+2, BC=2x+3,AC=3x-5. Find all possible values of x
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To solve the problem you need to solve all three "triangle inequalities":
AB + BC > AC, i.e. (x+2) + (2x+3) > 3x-5, (1)
AB + AC > BC, i.e. (x+2) + (3x-5) > 2x+3, (2) and
BC + AC > AB, i.e. (2x+3) + (3x-5) > x+2. (3)
(1) is equivalent to 5 > -5, which is always true and doesn't carry useful information;
(2) is equivalent to 4x-3 > 2x+3, i.e. 2x > 6, which means x > 3.
(3) is equivalent to 5x-2 > x+2, i.e. 4x > 4, which means x > 1.
So, you solved the problem. All possible values of x are x > 3.
It is the necessary and sufficient condition.
Answer. All possible values of "x" are determined by only one condition x > 3.