anonymous
  • anonymous
3x+(5/2)y=21 x+2y=14 can someone help me solve this plzzz.
Algebra
  • Stacey Warren - Expert brainly.com
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SOLVED
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chestercat
  • chestercat
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kropot72
  • kropot72
You can find x in terms of y by rearranging the second equation as follows: x + 2y = 14 Therefore: x = 14 - 2y Do you understand this first step?
anonymous
  • anonymous
your subtracting 2y from both sides?
kropot72
  • kropot72
Yes, you are correct. Now we can plug this expression for x into the first equation 3x + (5/2)y = 21 giving 3(14 - 2y) + (5/2)y = 21 which expands to 42 - 6y + (5/2)y = 21 Can you now solve this last equation to find the value of y?

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More answers

anonymous
  • anonymous
first I think is 21 - 42 which is -2. 6y + (5/2)y= -21 after that i'm kinda confused
UsukiDoll
  • UsukiDoll
\[3x+ \frac{5}{2}y=21\] \[x+2y=14\] I think dealing with the fraction is a chore... maybe we can multiply 2 throughout the first equation so we can have whole numbers to work with
anonymous
  • anonymous
yea im not good with fractions
UsukiDoll
  • UsukiDoll
\[3(2)x+ \frac{5(2)}{2}y=21(2)\] \[6x+ 5y=42\] \[x+2y=14\]
UsukiDoll
  • UsukiDoll
we could use subsitution by using the second equation x=14-2y and then plug it into the first equation
UsukiDoll
  • UsukiDoll
\[6(14-2y)+ 5y=42\]
kropot72
  • kropot72
The equation simplifies to - (7/2)y = -21 Now you can multiply both sides by -2 to give 7y = 42
anonymous
  • anonymous
6
kropot72
  • kropot72
yes y = 6 is correct.
UsukiDoll
  • UsukiDoll
\[84-12y+5y=42 \rightarrow 84-7y=42\] \[-7y=42-84 \rightarrow -7y=-42 \rightarrow y=6\]
UsukiDoll
  • UsukiDoll
yup y = 6
anonymous
  • anonymous
yay :D
UsukiDoll
  • UsukiDoll
so now we can plug y = 6 back into one of the equations.. let's try the second equation x+2y = 14
UsukiDoll
  • UsukiDoll
x+2(6)=14 x+12=14
kropot72
  • kropot72
Which shows there is more than one way to skin a cat, if you forgive the analogy :)
UsukiDoll
  • UsukiDoll
ewwww I own cats in real life
anonymous
  • anonymous
x=2 n I had a cat once
kropot72
  • kropot72
My bad form :(
UsukiDoll
  • UsukiDoll
yes so x = 2 and y = 6 we can plug it back into the original equations to see if we have the right answer.. I know we do because 2+2(6)=14 2+12=14 14=14
anonymous
  • anonymous
thank u
UsukiDoll
  • UsukiDoll
3(2) +5/2(6/1) = 21 6+(30/2)=21 6+15=21 21=21
anonymous
  • anonymous
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