Question

2(8u+2)=3(2u-7)
16u+4=6u-21
16u+4-6u=6u-21-6u
10u+4=(-21)
10u+4-4=(-21)-4
10u=-25
10u/10=-25/10
u=-2.5
how do i justify it

Answer 1

u just did

Answer 2

2(8u+2)=3(2u-7)


2(8(-2.5)+2)=3(2(-2.5)-7) ... replace ALL copies of 'u' with -2.5 (since u = -2.5)


2(-20+2)=3(-5-7)


2(-18)=3(-12)


-36=-36


Since the last equation is true, this verifies the answer

Answer 3

it doesn't get any more justified than that

Answer 4

Unfortunately @sonofa_nh it doesn't always justify since you could be introducing extraneous solutions that do not work

Answer 5

well the paper says to put it in seven lines
a.
b.
c.
d.
e.
f.
g.

Answer 6

does the idea make sense coraline?

Answer 7

eh...........no

Answer 8

I'm replacing all copies of the variable 'u' with -2.5 (since u is -2.5) and then evaluating like normal

Answer 9

at the end, I get a true equation, so u = -2.5 works

Answer 10

but how do i put it into seven lines?

Answer 11

Simple example:

solve x+2=4

solution is x = 2

check:

x+2 = 4

2+2 = 4

4 = 4 ... works

Answer 12

break up one line into two to make more lines

Answer 13

but what I wrote should be enough

Answer 14

ok i think i get it so i break up each line???

Answer 15

just enough to get 7 lines

Answer 16

a. 2(8u+2)=3(2u-7)


b. 2(8(-2.5)+2)=3(2(-2.5)-7)


c. 2(-20+2)=3(2(-2.5)-7)


d. 2(-20+2)=3(-5-7)


f. 2(-18)=3(-5-7)


e. 2(-18)=3(-12)


g. -36=-36

Answer 17

I'm basically streeeeetching it out to make it fit

Answer 18

thanks