Solving Systems of Equations by substitution-5x-8y=172x-7y=-17

2 answers:

6 0

$\left\{\begin{array}{ccc}-5x-8y=17\\2x-7y=-17\end{array}\right\\\left\{\begin{array}{ccc}-5x=8y+17&/\cdot(-2)\\2x-7y=-17&/\cdot5\end{array}\right\\\\\left\{\begin{array}{ccc}10x=-16y-34\\10x-35y=-85\end{array}\right\\\\substitute:\\\\-16y-34-35y=-85\\-51y=-85+34\\-51y=-51\ \ \ \ /:(-51)\\y=1\\\\10x=-16\cdot1-34\\10x=-50\ \ \ \ /:10\\x=-5\\\\Solution:x=-5\ and\ y=1$

masya89 [10]3 years ago

5 0

$-5x=17+8y \\ x= - \frac{17+8y}{5} \\ 2x-7y=-17 \\ 2* \frac{17+8y}{5} -7y=-17 \\ \frac{34+16y}{5} -7y=-17 \ we \ bring \ to \ the \ same \ denominator \ \\34+16y-35y=-85 \\ -19y=-85-34 \\ 19y=119 \\ y= \frac{119}{19} \\ x= -\frac{ 17+ 8* \frac{119}{19} }{5} \\ x= - \frac{ 17 + \frac{952}{19} }{5} \\ x= - \frac{ \frac{323+952}{19}}{5} \\ x= -\frac{ \frac{1275}{19} }{5} \\ x= -\frac{1275}{19} * \frac{1}{5} \\ x= -\frac{255}{19}$