document.write( "Question 1178678: Let a, b, and c be integers that satisfy 2a + 3b = 52, 3b + c = 41, and bc = 60. Find a+b+ c. \n" ); document.write( "
Algebra.Com's Answer #808024 by greenestamps(13200)![]() ![]() You can put this solution on YOUR website! \n" ); document.write( "(1) The fastest way to the answer: trial and error with simple mental arithmetic. \n" ); document.write( "Find pairs of integers b and c for which the product bc is 60, then find the pair for which 3b+c=41. Answer b=12, c=5. \n" ); document.write( "Then use 2a+3b=52 with b=12 to find a=8. \n" ); document.write( "And last a+b+c = 8+12+5 = 25. \n" ); document.write( "ANSWER: 25 \n" ); document.write( "(2) Using formal algebra.... \n" ); document.write( "3b+c=41 \n" ); document.write( "c = 41-3b \n" ); document.write( "bc = b(41-3b) = 60 \n" ); document.write( "41b-3b^2 = 60 \n" ); document.write( "3b^2-41b+60 = 0 \n" ); document.write( "Factor into the form \n" ); document.write( "(3b-m)(b-n) = 0 \n" ); document.write( "3b^2-(m+3n)+mn=0 \n" ); document.write( "We need mn=60 and m+3n=41.... \n" ); document.write( "Note that is exactly what we needed in solving the problem using trial and error -- so using the formal algebra didn't make solving the problem easier. \n" ); document.write( "However, assuming this question comes from a formal math course, you should know how to set up and solve the problem using the formal algebra. \n" ); document.write( "Continuing then... \n" ); document.write( "(3b-5)(b-12)=0 \n" ); document.write( "b = 5/3 (not an integer) or b=12; so b=12 \n" ); document.write( "Then, as before, c=5 and a=8. \n" ); document.write( " \n" ); document.write( " |