If $a$ is an odd integer and $b$ is an even integer. Which of the following is an odd integer?

เฉลยละเอียด

[STEP]Set $a=1$ and $b=2$ and check each choice[/STEP]

  • $5b=5(2)=10$ is even
  • $a+5=1+5=6$ is even
  • $2(a-b)=2(1-2)=-2$ is even
  • $a+4b=(1)+4(2)=9$ is odd
  • $2a-b=2(1)-(2)=0$ is even

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