Use substitution to decide whether -2 is a solution of 5(x + 4) -3(x+6) = 9(x + 1).

Question

If it is not a solution, explain why.  Want to know how to approach solution employing critical thinking. Easiest steps to do.

Answer 1

start: 5(x+4) -3(x+6) -9(x+1)   at x=-2

5x+20 -3x -18 -9x -9

(5x -3x -9x) + (20-18-9)

-7x  -7

at x=-2...-7*-2=+14

14-7=+7 not zero so -2 bad anser

Answer 2

When a question says use subtitution to decide if x=... ? Take the equation and put a (...) in place of all x's. In the given equation this would be; 5((-2)+4)-3((-2)+6)=9((-2)+1). Now you just process. 5(2)-3(4)=9(-1) 10-12=-9 -2=-9. NO! -2≠-9. Therefore x≠2 Basically this process is a "try it and see if it's true" process.