例1已知a,b满足方程组{a+5b=12,(1)3a-b=4,(2)则a+b的值是.分析对于这种解二元一次方程组的问题,直接的方法就是利用加减消元法或者代入消元法求解题目中的a,b,但仔细观察就会发现,只需计算a(1)+(2),不用解出a,b的值也可以得到+b的值.解(1)+(2),得(a+5b)+(3a-b)=12+4, (1) 3a-b = 4, (2) the value of a + b is 0. Analysis For the problem of solving a system of linear equations, The direct method is to use the addition or subtraction elimination method or substitution elimination method to solve the problem of a, b, but after careful observation, we can see that we only need to calculate a (1) + (2) without solving the values ​​of a and b The value of + b can also be obtained by solving (1) + (2) to obtain (a + 5b) + (3a-b) = 12 + 4,