Question

a și d repede va rogggggg va implor​

Answer 1

rezolvare sisteme de ecuatii prin metoda reducerii:

a)

$\begin{cases}-2x+9y=7 \ \ \Big|\cdot4 \\8x-5y=3 \end{cases} \iff \begin{cases}-8x+36y=28 \\8x-5y=3 \end{cases}$

$36y-5y=28+3 \iff 31y=31 \implies y = 1$

$8x-5=3 \iff 8x=8 \implies x = 1$

$\begin{cases}x = 1 \\y = 1 \end{cases} \implies \boxed {S = \Big\{(1;1)\Big\}}$

d)

$\begin{cases}3x-2y=13 \ \ \Big|\cdot2 \\8x+4y=16 \end{cases} \iff \begin{cases}6x-4y=26 \\8x+4y=16 \end{cases}$

$8x+6x=26+16 \iff14x=42 \implies x = 3$

$9-2y=13 \iff 2y=-4 \implies y = -2$

$\begin{cases}x = 3 \\y = -2 \end{cases} \implies \boxed {S = \Big\{(3;-2)\Big\}}$