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Question

Mathematics Question on linear inequalities in one variable

The values of x satisfying x4+x9=5| x - 4 | + | x - 9 | = 5, is :

A

x = 4, 9

B

4 \leq x \leq 9

C

x \leq 4 or x \geq 9

D

none of these

Answer

4 \leq x \leq 9

Explanation

Solution

Consider the given equation x4+x9=5 {| x - 4 | + | x - 9 | = 5} {4x+9x=5x4 x4+9x=54<x9 x4+x9=5x>9\Rightarrow \:\: \begin{cases} { 4 - x + 9 - x = 5} & {x \leq 4} \\\ { x - 4 + 9 - x = 5} & { 4 < x \leq 9}\\\ {x - 4 + x - 9 = 5} & {\quad x > 9} \end{cases} {x=4x4 5=54<x9 x=9x>9\Rightarrow \:\: \begin{cases} { x = 4 } & {x \leq 4} \\\ { 5 = 5} & { 4 < x \leq 9}\\\ {x = 9} & {\quad x > 9} \end{cases} So, 4x9 { 4 \leq x \leq 9}