Question

-4x + 9 = -7x - 12

+7 +7x
3x + 9 = 12
-9 -9
3x/3 = 3/3
x = 1
What is the error? How to fix the mistake. Solve the equation.​

Answer 1

Explanation:

-4x+9=-7x-12

9=-3x-12

21=-3x

x= -7

At the beginning of the solved equation, they added 7 to -4x and 7x to 9, you are not able to add numbers in equations unless they are like terms. You could only add 7x to 4x and the 7, in the beginning, adding to -4x came out of nowhere. To fix the mistake you need to add like terms.