The sum of a squared and b is given by
\(a^2+b\)
7 times the sum of a squared and b is given by
\(7(a^2+b)\)
while 4 times the sum of a squared and b is given by
\(4(a^2+b)\)
Therefore, 7 times the sum of a squared and b minus 4 times the sum of a squared and b is given by
\(7(a^2+b)-4(a^2+b)=3(a^2+b)\)
