90% of Math Students Make This ERROR!!!

How to avoid making a common algebra mistake.

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TC Math Notes

[larrystuder]

Multiply both sides by 3. Giives x+1 = (1/5) x 3 or 3/5. 3/5 -1 = -2/5= x done..

[davidhitchen]

Multiply both sides by 3. Subtract 1 from both sides. To hell with cross products.

[argonwheatbelly]

x=-2/5 in about eight seconds in my head. Sorry it was so slow. Nice video.

[MultiThinkingMan]

Wow, I can’t think of a harder way to explain this or solve the problem. Good work.

[CabinFever]

Multiply both sides by 3, so: x+1 = 3/5 : subtract 1 from both sides: x = -2/5. That's the way we learned it 50+ years ago.

[Number_]

The guy is right! I see a lot of people getting this wrong. This is basic. Mulitply by 5 then by 3 and solve for x. Simples.

[bobcornwell]

I multiplied both sides by 3 to get rid of the denominator under the sum-term. I then subtracted 5/5ths from both sides.

[ModeratelyAmused]

I have a hard time believing a majority of students would have even tried to find the common denominator, little alone come to the conclusion that, 5 times (X +1) = 5X + 1. If this guy is a teacher and he isn't teaching them to start by multiplying both sides by 3, it's no wonder his students are confused.

[davidely]

My solution was a little more ... old school? I multiplied both sides by 3, canceled the 3 on the left side, subtracted 1 (or 5/5) from both sides and found x=(-2/5) (3/5-5/5=(-2/5)) I like the cross multiplication method presemted here even more.. Nicely done! ❤

[LarcR]

You over explain so much that you make things sound more difficult than they actually are.

[raystormont]

I use your problems as mind puzzles by solving almost all without pencil or calc. as a chalenge in my head as math exercise and have become addicted, Thanks for the puzzles with the answer at beginning. Ray

[TikkyTakMoo]

I'm going to mention this method because it hasn't been, and it's also a handy trick for reconstructing equations if you ever want to dismantle the physical world..
if:
a/b = c/d ;
a/c = b/d
ex:
1/3 = 2/6 ;
1/2 = 3/6

(X+1)/3 = 1/5;
X+1 = 3/5 ;
X = 3/5 - 5/5 = -⅖

ik this is basic stuff, but it's useful and often forgotten.

[aleleeinnaleleeinn]

I cross multiplied
I lft the x+1 in parenthesis 5(z+1) = 3
Divide both sides by 5
x+1 -3/5
subtract 1 from both sides
x = -2/5

[mikehigbee]

I got the right answer by the easier method others used. However, I didn't know, or had forgotten, about the cross product relationship of equivalent fractions. So I learned, or relearned, something. Thanks.

[harrymatabal]

X+1 = 3/5. X =-2/5. Simpler than your method

[jakobgruber]

I'm no math genius but I can solve this equation in 2 seconds in my head.

[johng.]

when you use the vinculum that is a bracket, when you put that in a single line it becomes (x+1)/3 because the vinculum is a grouping symbol

[duggydugg]

the x + 1 is a term... if you are multiplying, you have to multiply all parts of the term.. no matter how many parts

[henkhu]

Can you please give us the data from which you conclude that 90% of math students make this mistake?

[robertstuart]

The simplest means of solving is to clear the denominators multiplying by 15. You get 5x = -2, and x = -2/5.