Question

Solve the equation by factoring.5z2 − 21z + 4 = 0A.) z = 1 or z = 4B.) z = or z = –4C.) z = 1 or z = –4D.) z = or z = 4Use format,

Answer 1

D) z = 1/5 or z = 4

Explanation:

We have the following equation:

`5z^2-21z+4=0`

We solve by factoring like this:

`\begin{gathered} 5z^2-21z+4=0 \\ -21z=-z-20z \\ 5z^2-z-20z+4=0 \\ z(5z-1)-4(5z-1)=0 \\ (5z-1)(z-4)=0 \\ 5z-1=0\rightarrow z=(1)/(5) \\ z-4=0\rightarrow z=4 \end{gathered}`

Therefore, the solution of the equation is z = 1/5 or z = 4