start by bringing all terms to the left of the equation
[tex]3x^2-14x+15=0[/tex]multiply the equation by the leading coefficient
[tex]9x^2-42x+45=0[/tex]use a substitution u=3x, because it is the square root of the first term,
[tex]u^2-14u+45=0[/tex]factor using the solutions -9 and -5 since multiplied together they give a result of 45 and added together -14
[tex](u-9)(u-5)[/tex]replace with the substitution used
[tex](3x-9)(3x-5)[/tex]then, divide by the 3 we multiplied in the first step
[tex](x-3)(3x-5)[/tex]Answer:
[tex](x-3)(3x-5)[/tex][tex]\begin{gathered} 3x^2-5x-9x+15 \\ 3x^2-14x+15 \end{gathered}[/tex]