Answer to Question #262189 in Discrete Mathematics for abhi

Question

Prove or disprove : for every real number x, |x − 8| + x ≥ 6.

Answer 1

If $x>8$ , then $|x-8|+x=x-8+x=2x-8>2\cdot 8-8=8$ .

If $x\leq 8$ , then $|x-8|+x=8-x+x=8$ .

We have that $| x-8|+x\geq 8$ .

Since $8>6$ , it follows that $|x-8|+x\geq 6$ for every real number $x$ .