A graph of \(\log y\) against \(\log x\)

 The variables \(x\) and \(y\) and the constants \(a\) and \(b\) are real and positive. The variables \(x\) and \(y\) are related.

A graph of \(\log y\) against \(\log x\) is drawn.

For which one of the following relationships will this graph be a straight line?

• \(y^6 = a^x\)
• \(y = ab^x\)
• \(y^2 = a + x^b\)
• \(y = ax^b\)
• \(y^x = a^b\)