How do you solve #4x+ 8=-4#?

1 Answer
Feb 29, 2016

x=-3

Have a look at how the first principles method work. The shortcut is a shortened version of it!

Explanation:

Given:#" "4x+8=-4#

#color(blue)("Shortcut method")#

Move the 8 to the other side of the equals

#4x=-4-8#

Move the 4 from #4x# to the other side of the equals

#x=(-4-8)/4 = (-12)/4=-3 #

'~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("Using first principles method")#

Subtract #color(blue)( 8)# from both sides

#color(brown)(4x+8color(blue)(-8)= -4color(blue)(-8))#

#4x+0=-12#

Divide both sides by 4. This is the same as #color(blue)(xx1/4)#

#color(brown)(4xcolor(blue)(xx1/4)=(-12)color(blue)(xx1/4))#

#color(brown)(4/(color(blue)(4)) xx x=(-12)/(color(blue)(4)))#

But #4/4 = 1" and "(-12)/4 = -3# giving

#color(magenta)(x=-3)#