How do you solve the following system?: 3x +y =15 , -9x +8y = 43x+y=15,−9x+8y=4

1 Answer
Anjali_Sharma
Jul 30, 2016

There are many ways to solve this.I'm using substitution method.
lets see:

Explanation:

3x+y=153x+y=15
impliesy=15-3x(equation 1)⇒y=15−3x(equation1)

putting the value of y in equation 2
-9x+8(15-3x)=4−9x+8(15−3x)=4
implies-9x+120-24x=4⇒−9x+120−24x=4
implies-33x=-116⇒−33x=−116
impliesx=(-116)/-33⇒x=−116−33
impliesx=3.51⇒x=3.51

putting the value of x in equation 1
y=15-3*3.51y=15−3⋅3.51
impliesy=15-10.53⇒y=15−10.53
impliesy=4.47⇒y=4.47

therefore x=3.51 and y=4.47

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