For what values of x is the following equation satisfied : 3x+9 = 21+7x ?
[latex] 3x+9 = 21+7x\\ 4x=-12\\ x=-3[/latex]
First of all, the first power of 'x' is the highest power in the whole equation,
so we only expect one solution.
You said that 3x+9 = 21+7x
Subtract 3x from each side:
9 = 21 + 4x
Subtract 21 from each side:
-12 = 4x
Divide each side by 4 :
-3 = x