Logic Synthesis Synthesis - Consensus property?
\$x_1x_2'x_3'x_4' + x_1x_2'x_3'x_4 + x_1x_2x_4 + x_1x_2'x_3x_4'\$

Repeating first term : a = a+a

\$x_1x_2'x_3'x_4' + x_1x_2'x_3'x_4' + x_1x_2'x_3'x_4 + x_1x_2x_4 + x_1x_2'x_3x_4'\$

Associativity : 

\$x_1x_2'x_3'x_4' + x_1x_2'x_3'x_4 + x_1x_2'x_3'x_4' + x_1x_2'x_3x_4' + x_1x_2x_4\$

=
\$x_1x_2'x_3'(x_4' + x_4) + x_1x_2'(x_3' + x_3)x_4' +  x_1x_2x_4\$

Simplification : a + a' = 1

\$x_1x_2'x_3' + x_1x_2'x_4' + x_1x_2x_4\$