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Mathematics 8 Online
OpenStudy (stephanos100):

PLSSS HELP!!! MEDALS!!! Find all solutions to the following equation.

OpenStudy (stephanos100):

\[\sqrt{4x-3} +2=7\]

jimthompson5910 (jim_thompson5910):

The first thing you need to do is get the square root all by itself on one side That means you'll have to subtract 2 from both sides

OpenStudy (stephanos100):

okay and then what

jimthompson5910 (jim_thompson5910):

subtract 2 from both sides \[\Large \sqrt{4x-3} +2=7\] \[\Large \sqrt{4x-3} +2{\color{blue}{-2}}=7{\color{blue}{-2}}\] \[\Large \sqrt{4x-3} +0=5\] \[\Large \sqrt{4x-3}=5\]

OpenStudy (stephanos100):

right

jimthompson5910 (jim_thompson5910):

now you need to undo that square root. What operation is the opposite of square rooting?

OpenStudy (stephanos100):

squared

jimthompson5910 (jim_thompson5910):

yes, square both sides and you'll get what equation?

OpenStudy (stephanos100):

4x-3=25

jimthompson5910 (jim_thompson5910):

good

jimthompson5910 (jim_thompson5910):

now solve for x like normal (that you've done previously with solving linear equations)

OpenStudy (stephanos100):

so x=7

OpenStudy (stephanos100):

can i ask you a question though

jimthompson5910 (jim_thompson5910):

x = 7 is the possible answer Make sure you plug this back into the original equation to check and confirm it

jimthompson5910 (jim_thompson5910):

`can i ask you a question though` yes go ahead

OpenStudy (stephanos100):

why can't you just square the equation on both sides form the get go

jimthompson5910 (jim_thompson5910):

You can. There's nothing stopping you. But it just makes everything more complicated than it has to be.

OpenStudy (stephanos100):

but when i did it that way I got x=12

OpenStudy (stephanos100):

so i'm not sure what i did wrong

jimthompson5910 (jim_thompson5910):

hmm that's not correct. Show me your steps of what you did

OpenStudy (stephanos100):

alright its obviously wrong but \[(\sqrt{4x-3}+2)^{2}=(7)^{2}\] \[4x-3+4=49\]

jimthompson5910 (jim_thompson5910):

you made an error when you squared the left side

jimthompson5910 (jim_thompson5910):

it's tempting to think that (x+y)^2 = x^2+y^2, but that's not a true fact

jimthompson5910 (jim_thompson5910):

instead it's really (x+y)^2 = x^2 + 2xy + y^2 you have to use FOIL here

OpenStudy (stephanos100):

yeah i just realized that after typing it out thanks a bunch

jimthompson5910 (jim_thompson5910):

no problem

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