Question 387743
{{{(4sqrt(5) - 12sqrt(7) )*(5sqrt(5) + 15sqrt(7) )}}}
Multiply the terms the same as in any multiplication of binomials.  FOIL, etc.
= {{{4*5*sqrt(25) + 4*15*sqrt(35) - 60sqrt(35) -180sqrt(49)}}}
= {{{20*5 + 60sqrt(35) - 60 sqrt(35) - 180*7}}}
= 100 - 1260
= -1160