Question

find the solution of this system of equation.
-3x-7y=-66 and -10x-7y=-24

Answer 1

\[-3x-7y=-66\]\[-10x-7y=-24\]by elimination method, take eq2 fram eq1

Answer 2

\[7x=-42\]

Answer 3

solve for x

Answer 4

\[A = \left[\begin{matrix}-3 & -7 \\ -10 & -7\end{matrix}\right]\]
\[B = \left(\begin{matrix}x \\ y\end{matrix}\right)\]
\[C = \left(\begin{matrix}-66 \\ -24\end{matrix}\right)\]
\[A ^{-1}C = B\]

Answer 5

x=-42/7

Answer 6

Find the inverse of matrix A and multiply it with C and you get your answer.

Answer 7

then sub x=?? into the 1st eq. to find for y

Answer 8

what did u get for x @Eadorno

Answer 9

I got x=6 is that correct @LynFran

Answer 10

it shd be -6

Answer 11

x=-42/7
x=-6

Answer 12

\[|A| = (-3*-7)-(-7*-10)\]\[A ^{-1} = \frac{ 1 }{ |A| }\left[\begin{matrix}-3 & -7 \\ -10 & -7\end{matrix}\right] = \left[\begin{matrix}\frac{ 1 }{ 7 } & \frac{ -1 }{ 7 } \\ \frac{ -10 }{ 49 } & \frac{ 3 }{ 49 }\end{matrix}\right]\]
\[A ^{-1}C = \left[\begin{matrix}\frac{ 1 }{ 7 } & \frac{ -1 }{ 7 } \\ \frac{ -10 }{ 49 } & \frac{ 3 }{ 49 }\end{matrix}\right]\left(\begin{matrix}-66 \\ -24\end{matrix}\right) = \left(\begin{matrix}-6 \\ 12\end{matrix}\right)\]

Answer 13

to find y
-3(-6)-7y=-66
18-7y=-66
18+66=7y
84=7y
84/7=y
12=y
i like your matrix method too @saseal

Answer 14

nice thank you both @saseal @LynFran

Answer 15

welcome

Answer 16

welcome

Answer 17

@LynFran It's my favorite method so far, works every time.