Erica has 7 coins worth $1.55. If the coins are all quarters and nickels, how many quarters and nickels does she have?
1 answer:
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Answer:
x= -3 and y= 0
Step-by-step explanation:
5x+2y=-15
<u>2x-2y=-6 </u>
<u>7x =-21</u>
x= -3
Putting value of x in equation 1
5(-3) +2y=-15
-15+2y= -15
2y= 0
y= 0
This can be solved with the help of matrices
In matrix form the above equations can be written in the form
=
Let
= A
= X and
= B
Then AX= B
or X= A⁻¹ B
where A⁻¹= adj A/ ║A║ where mod A≠ 0
adj A=
║A║= ( 5*-2- 2*2)= -10-4= -14≠0
X= A⁻¹ B
=- 1/14
=- 1/14
=- 1/14
=- 1/14
=
=
From here x= -3 and y= 0
Solution Set = [(-3,0)]