Question

Hlo Brainlians !

Question :-
→ Solve these simultaneous equations :

» y = 9 - 2x , y = x - 12


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Answer 1

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Q U E S T I O N :—

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Solve these simultaneous equations :-

→ y = 9 - 2x , y = x - 12.

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A N S W E R :—

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Given :

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• y = 9 - 2x , y = x - 12.

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To Find :

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• Solve these simultaneous equations.

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Here, first we will solve the 1st equation then substitute the 2nd equation into the 1st equation. It means that we will write the answer that we got while solving the 1st equation in place of x. Than, we will get the value of y in 2nd equation. With the help of the value of y in the 2nd equation we will find the value of x in the 1st equation.

★ Note :-

In 1st equation we will move the x from the RHS of the 1st equation to LHS so that there won't be any confusion in solving the 2 given equations.

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S O L U T I O N :—

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★ 1st equation :

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$\bf{ →y = 9 - 2x } \\ \\ \bf{→2x = 9 - y} \\ \\ \bf{→x = \frac{9 - y}{2} }$

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★ Substituting the 2nd equation into the 1st :

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$\bf{→y = x - 12} \: \: \: \: \: \: \: \: \\ \\ \bf{→y = \frac{9 - 4}{2} - 12 } \\ \\ \bf{→y = \frac{9 - y - 24}{2} } \\ \\ \bf{→y = \frac{9 - 24 - y}{2} } \\ \\ \bf{→y = \frac{ - 15 - y}{2} \: \: \: \: \: } \\ \\ \bf{→2y = - 15 - y} \\ \\ \bf{→2y + 2y = - 15} \\ \\ \bf{→3y = - 15} \: \: \: \: \: \: \: \: \: \: \: \\ \\ \bf{→y = \frac{ - 15}{3} \: \: \: \: \: \: \: \: \: \: \: \: \: } \\ \\ \bf{→y = - 5 \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: }$

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★ Putting the value of y = -5 in 1st equation.

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$\bf{→x = \dfrac{9 - y}{2} } \\ \\ \bf{→x = \frac{9 + 5}{2} } \\ \\ \bf{→x = \frac{14}{2} } \: \: \: \: \: \\ \\ \bf{→x = 7} \: \: \: \: \: \: \:$

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Answer 2

Given :-

y = 9 - 2x

y = x - 12

To Find :-

Value of x and y

Solution :-

As

y = y

Therefore

9 - 2x = x - 12

9 - 12 = x - 2x

-3 = -x

3 = x

Therefore value of x is 3 and

9 - 2(3)

9 - 6

-3