Study Guide: Systems of Linear Equationsmrrogove.weebly.com/uploads/4/3/0/0/43009773/g8m4_sg...A...

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Name:_________________________ Math ________, Period __________ Mr. Rogove Date: __________ G8M4: Study Guide Systems of Linear Equations 1 Study Guide: Systems of Linear Equations Systems of Linear Equations A system of linear equations is when two or more linear equations are involved in the same problem. The solution for a system of linear equations is the ordered pair (, ) that makes BOTH equations true. Solutions to systems of linear equations: Systems of equations either have one unique solution, no solution, or infinitely many solutions. One Unique Solution: If two linear equations have different slopes, there will be one unique solution, which is at the point of intersection. No Solutions: If two linear equations have the same slope, but different y-intercepts, the lines are parallel and there is NO solution to the system of equation because there is no point of intersection. Infinitely Many Solutions: If two linear equations have the same slope AND the same y-intercept, the two lines are identical and the system will have infinitely many solutions. Solving Systems of Equations: Graphing On a coordinate plane, the intersection (coordinate pair) of two lines is the solution to a system of linear equations. Example: The solution to the system of equations below is (1, 2) The equation for ! is = 2. Substitute (1,2) into the linear equation to make sure that the point IS on the line. The equation for ! is = + 3. Substitute (1,2) into the linear equation to make sure that the point IS on the line. ! !

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Page 1: Study Guide: Systems of Linear Equationsmrrogove.weebly.com/uploads/4/3/0/0/43009773/g8m4_sg...A system of linear equations is when two or more linear equations are involved in the

Name:_________________________ Math________,Period__________

Mr.Rogove Date:__________

G8M4:StudyGuideSystemsofLinearEquations1

Study Guide: Systems of Linear Equations

Systems of Linear Equations

Asystemoflinearequationsiswhentwoormorelinearequationsareinvolvedinthesameproblem.Thesolutionforasystemoflinearequationsistheorderedpair(𝑥,𝑦)thatmakesBOTHequationstrue.Solutions to systems of linear equations:Systemsofequationseitherhaveoneuniquesolution,nosolution,orinfinitelymanysolutions.OneUniqueSolution:Iftwolinearequationshavedifferentslopes,therewillbeoneuniquesolution,whichisatthepointofintersection.NoSolutions:Iftwolinearequationshavethesameslope,butdifferenty-intercepts,thelinesareparallelandthereisNOsolutiontothesystemofequationbecausethereisnopointofintersection.InfinitelyManySolutions:IftwolinearequationshavethesameslopeANDthesamey-intercept,thetwolinesareidenticalandthesystemwillhaveinfinitelymanysolutions.

Solving Systems of Equations: Graphing Onacoordinateplane,theintersection(coordinatepair)oftwolinesisthesolutiontoasystemoflinearequations.Example:Thesolutiontothesystemofequationsbelowis(1, 2)

Theequationfor𝑙! is 𝑦 = 2𝑥.Substitute(1,2)intothelinearequationtomakesurethatthepointISontheline.Theequationfor𝑙! is 𝑦 = −𝑥 + 3.Substitute(1,2)intothelinearequationtomakesurethatthepointISontheline.

𝑙!𝑙!

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Solving Systems of Equations: Substitution

Systemsofequationscanbesolvedbysubstitutinganexpressionfromoneequationintotheotherequation.Examples:1.

𝑦 =32 𝑥 − 4

𝑦 = −𝑥 + 9

Sinceyisequaltoboth(!!𝑥 − 4) 𝐀𝐍𝐃(−𝑥 + 9),thosetwo

expressionsareequaltoeachother…

32 𝑥 − 4 = −𝑥 + 9

Tosolvethesystem,solveforx,andthensubstituteyoursolutionforxintooneofyouroriginalequationsandsolvefory.

2.𝑦 = 2𝑥 − 13𝑥 + 2𝑦 = 6

Sinceyisisolatedinthefirstequation,wecansubstitute“2𝑥 − 1”whereverweseeyinthesecondequation:

3𝑥 + 2 2𝑥 − 1 = 6Tosolvethissystem,wecansolveforx,andthensubstituteyoursolutionforxintooneoftheoriginalequationsandsolvefory.

WHENTOSOLVEUSINGSUBSTITUTION:

1.Whenbothequationsarealreadyinslopeinterceptform(asinexample1above)2.Whenonevariableisisolatedinoneofthelinearequations(asinexample2above)

Solving Systems of Equation: Elimination SolvesystemsoflinearequationsusingeliminationbyADDINGequationstoeliminateavariable.NOTE:YoumightneedtomultiplyanENTIREequationbeforeyoucanaddthetwoequationstoeliminateavariable.Examples:

6𝑥 − 5𝑦 = 212𝑥 + 5𝑦 = −5

Since5𝑦 and − 5𝑦areopposites,ifweaddthetwoequationstogether,wecaneliminatethey-variable.

8𝑥 + 0𝑦 = 16Fromhere,solveforx,andthensubstituteyoursolutionforxintooneofyouroriginalequationsandsolvefory.

6𝑥 − 4𝑦 = 182𝑥 + 3𝑦 = 4

Sincetherearenoopposites,multiplythesecondequationby−3(tocreateasituationwhereyouhaveopposites(6𝑥 and − 6𝑥)andthenfollowthestepsintheexampleontheleft.

6𝑥 − 4𝑦 = 18−6𝑥 − 9𝑦 = −12

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The Problem Set CompletetheproblemsbelowandturnthissheetinpriortocompletingtheassessmentDeterminewhethereachofthefollowinghaveoneuniquesolution,infinitelymanysolutionsornosolutions.DoNOTsolvethesystem,butexplainHOWYOUKNOWthenumberofsolutionsinonesentence.

𝑦 =34 𝑥 + 12

3𝑥 − 4𝑦 = 48

4𝑥 − 2𝑦 = −7

𝑦 =12 𝑥 − 14

𝑥 = 3𝑦 − 42𝑥 + 6𝑦 = 12

7𝑦 = 14𝑥 − 214𝑥 − 2𝑦 = 6

SolvethefollowingusingEITHERsubstitutionorelimination—yourchoice.Whicheveryouchoose,writeasentenceexplainingWHYyouselectedthemethodyoudid.

𝑦 = 2𝑥 − 1𝑥 + 3𝑦 = 9

2𝑥 − 5𝑦 = 94𝑥 + 2𝑦 = 3

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𝑦 = 𝑥 − 4𝑥 + 𝑦 = 4

𝑥 + 3𝑦 = 144𝑥 − 6𝑦 = 2

Solvethefollowingwordproblems.Bananashave105calorieseach.Appleshave75calorieseach.Inoneday,Maryonlyeatsthosetwofruits,andsheeats13piecesoffruit,andconsumesatotalof1215calories.HowmanyofeachfruitdidMaryconsume?Howdoyouthinkherstomachfeels?

OniTunes,youcandownloadsongsfor$1.29,andrentHDmoviesfor$5.99each.IfDominicspends$63.40for20totalpiecesofmedia(thisincludesbothmoviesandsongs),howmanymoviesdidherent?Howmanysongsdidhedownload?

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Solvethefollowingsystemsofequationsbygraphing,usingsubstitution,andusingelimination.

𝑦 = −32 𝑥 + 1

3𝑥 − 4𝑦 = 12

Solvebysubstitution:Solvebyelimination:

𝑥 − 𝑦 = −1𝑦 = 3𝑥 + 2

Solvebysubstitution:Solvebyelimination: