Question

The gradient of the line joining the points (9,a) and (2a,1) is 2/a where a is not equal to 0. Calculate the possible values of a.

Ans: 3 or -6 but I can't get the answer.

Answer 1

\[\frac{a-1}{9-2a}=\frac{2}{a}\] is what you need to solve

Answer 2

\[a(a-1)=2(9-2a)\]
\[a^2-a=18-4a\]
\[a^2+3a-18=0\] etc

Answer 3

\[3^2+18=0\]

Answer 4

18^2 has a A

Answer 5

so solve for a