Question 1206885

{{{u = 5i + j}}}
{{{v = i - 3j}}}  
{{{w = 3i + 7j}}}


{{{u*(v+w)}}}

first find {{{v+w=i-3j+3i+7j=4i+4j}}}


{{{u*(v+w)=(5i + j)*(4i+4j)}}}

{{{u*(v+w)=5i*4i+5i*4j+j*4i+j*4j}}}


since  {{{i*i = 1}}}, {{{j*j =1}}}, {{{i*j = 0}}},{{{ j*i =0}}}, we have


{{{u*(v+w)=5*4*1+5*4*0+0*4+1*4}}}

{{{u*(v+w)=24}}}