Question 63631This question is from textbook An Incremental Development
: please help me to solve the following
Use substitution to solve
4x + y = 17 and 3x - 5y = 30
This question is from textbook An Incremental Development
Answer by funmath(2933)   (Show Source):
You can put this solution on YOUR website! Use substitution to solve
E1: 4x + y = 17
E2: 3x - 5y = 30
Solve E1 for y and substitute it into E2 for y and solve for x.
E1: -4x+4x+y=-4x+17 --> y=-4x+17
E2: 3x-5(-4x+17)=30
3x+20x-85=30
23x-85=30
23x-85+85=30+85
23x=115
23x/23=115/23
x=5
Substitute x=5 into E1 and solve for y:
E1: 4(5)+y=17
20+y=17
-20+20+y=-20+17
y=-3
The solution: (x,y)=(5,-3)
Check the solution by substituting 5 in for x and -3 in for y in both equations and see if the equations balance.
E1: 4(5)+(-3)=17
20-3=17
17=17 E1 checks.
E2: 3(5)-5(-3)=30
15+15=30
30=30 E2 also checks, so we know we're right!
Happy Calculating!!!
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