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how replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions as the one shown. 8x + 7y = 39. 4x – 14y = –68.

The student is unable to show that (3, 4) is a solution of the given system. ... of that equation and a multiple of the other produces a system with the same solutions. ... Explain that when one equation in a system is replaced by the sum of that ...

Answer with Step-by-step explanation:

Consider the system of equation

[tex]8x+7y=39[/tex].....(1)

[tex]4x-14y=-68[/tex]...(2)

Now, multiply equation (1) by 2 and we get

[tex]16x+14y=78[/tex]...(3)

[tex]4x-14y=-68[/tex] ...(2)

Adding equation (3) with equation (2)

Then, we get

[tex]20x=10[/tex]..(4)

[tex]x=\frac{10}{20}=\frac{1}{2}[/tex]

Now, substitute [tex]x=\frac{1}{2}[/tex] in equation (2)

[tex]4(\frac{1}{2})-14y=-68[/tex]

[tex]2-14y=-68[/tex]

[tex]-14y=-68-2=-70[/tex]

[tex]y=\frac{70}{14}=5[/tex]

Equation (2) and equation (4)   intersect at point ([tex]\frac{1}{2},5)[/tex].

Therefore, the solution of equation (2) and equation (4)

is ([tex]\frac{1}{2},5)[/tex].

Substitute [tex]x=\frac{1}{2}, y=5[/tex] in equation (1)

Then, we get

[tex]8(\frac{1}{2})+7(5)=4+35[/tex]

[tex]4+35=39[/tex]

LHS=RHS

It means [tex](\frac{1}{2},5)[/tex]) is a solution of equation (1).

Substitute [tex]x=\frac{1}{2}[/tex] y=5 in equation (2)

Then, we get

[tex]4(\frac{1}{2})-14(5)=2-70=-68[/tex]

LHS=RHS

Therefore, the point [tex](\frac{1}{2},5)[/tex] satisfied the equation (1) and equation (2).

Hence, the solution of equation (1) and equation (2) is ([tex]\frac{1}{2},5)[/tex].

We can say that solution of equation (1) and equation (2) and equation (2) and equation (4) is same.