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maw [93]
3 years ago
8

Solve the following system of equations -7x+2y=9, -8x+9y=17

Mathematics
2 answers:
emmasim [6.3K]3 years ago
5 0
\left\{\begin{array}{ccc}-7x+2y=9&|\cdot9\\-8x+9y=17&|\cdot(-2)\end{array}\right\\  \left\{\begin{array}{ccc}-63x+18y=81\\16x-18y=-34\end{array}\right\ |\text{add both sides of equations}\\-47x=47\ \ \ |:(-47)\\.\ \ \ \ x=-1\\\\\text{substitute the value of x to the first equation}\\\\-7(-1)+2y=9\\7+2y=9\ \ \ |-7\\2y=2\ \ \ |:2\\y=1\\\\\text{Answer:}\ x=-1\ and\ y=1\to(-1;\ 1)
umka21 [38]3 years ago
3 0
<span>-7x+2y=9  | * 9</span>
<span>-8x+9y=17  | *(-2)
</span>

<span>-63x + 18y = 81</span>
<span>16x -18y = -34
</span>
<span>_______________ +
</span>
<span>-47x = 47 ⇒ x = -1
</span>

<span>7+2y=9 ⇒ 2y = 9-7 ⇒ y = 1
</span>
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