2 Yuan's 1 degree equation, each equation has two variables, so we must find a way to get rid of one, so that we can solve it directly. If you remove a variable, this is elimination.
Secondly, substitution elimination is a kind of elimination, and the way is substitution. Replace what? Substituting one of the variables, what do you think of the following:
An equation, such as (1), 5x+ 80 = 6y+20, can be solved no matter what Y is, and 5x = 6y-60 =>;; x = 1.2y - 12
This is an expression of x, with the variable y in it. It doesn't matter, this expression is obtained from equation 1, because it is the expression of X, so we have to substitute X into equation 2:
4y = 2x+80 = 2 *( 1.2y- 12)+80 = & gt; 4y = 2.4y -24 + 80 = > 1.6y = 56
= & gty = 35
Note: Why can't the equation 1 be brought in? Because the expression derived from equation 1 replaces equation 1, only the result of 0=0 can be obtained, which cannot be used to solve y, but it can be used to verify whether the expression is wrong.
Find y again, and then calculate x according to the expression: x =1.2y-12.
x = 1.2y- 12 = 1.2 * 35- 12 = 30
Finally, you can not do it. Substitute X = 30 and Y = 35 into the original equation to check.
Summary: In short, the steps are as follows
1) Derive the expression of X = containing y or Y = containing x from 1 equations.
2) Substitute the variables on the left side of the expression into another equation to get a unary equation. Solve this variable
3) Substitute the solution result into the expression to get the solution of another variable.
4) check