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Solve each system of equations

r+s+t=52r−7s−3t=1312r−13s+23t=−1

Short Answer

Expert verified

The solution set of the given system of equations is .(8,3,−6)

Step by step solution

01

– Use the elimination method to get the system of equations in two variables.

Multiply the equation r+s+t=5by 3and add the new resultant equation to the equation 2r-7s-3t=13.

 â¶Ä‰r+ â¶Ä‰â€‰s+ â¶Ä‰t= â¶Ä‰â€‰52r−7s−3t=13_ â¶Ä‰â€‰â¶Ä‰multiplyby3→ â¶Ä‰3r+3s+3t=152r−7s−3t=13_ â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰5r−4s+ 0= 28

So, the resultant equation is 5r-4s=28.

Next, multiply the equation r+s+t=5by 4and multiply the equation 12r-13s+23t=-1by 6.

Then subtract the two new resultant equations

 â¶Ä‰â€‰r+ â¶Ä‰â€‰s+ â¶Ä‰â€‰â¶Ä‰t= â¶Ä‰512r−13s+23t=−1_ â¶Ä‰â€‰â¶Ä‰multiplyby4→multiplyby6→ â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰4r+4s+4t=20(−)3r−2s+4t=−6_ â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰r+6s+ â¶Ä‰â€‰0=26

So, the resultant equation is r+6s=26

02

– Use the elimination method to solve the system of two equations.

Multiply 5r-4s=28by 3 and multiply the equation r+6s=26by 2.

Then add the two new resultant equations.

5r−4s=28 â¶Ä‰r+6s=26_ â¶Ä‰â€‰â¶Ä‰multiplyby3multiplyby2 â¶Ä‰15r−12s=84 â¶Ä‰2r+12s= 52_ â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰17r+ â¶Ä‰â€‰â¶Ä‰â€‰0=136

Solve 17r=136for r:

17r=13617r17=13617 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰Dividebothsidesby17r=8

03

– Find the values of sand t.

Substitute$r=8$in\[r+6s=26\]and find the value of s.

r+6s=268+6s=26 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰Substitute8forr6s=18 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰Subtract8frombothsidess=3 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰Dividebothsidesby6

Substitute r=8,s=3inr+s+t=5and find the value of t.

r+s+t=58+3+t=5 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰substitute8forr,3fors11+t=5 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰simplifyt=−6 â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰â€‰â¶Ä‰Subtract11 f°ù´Ç³¾²ú´Ç³Ù³ó²õ¾±»å±ð²õ

Hence, the solution of the given system of equations isr,s,t=8,3,-6.

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