Mathematics: 7x+8y=-18, 4x-9y=-3 solve the system of equations

7x+8y=-18, 4x-9y=-3 solve the system of equations - id78184934967, taleiayarbough4544

Ответ:

jdkrisdaimcc11

09.03.2022

$\large\boxed{x=6,\ y=3\to(6,\ 3)}$

Step-by-step explanation:

$\left\{\begin{array}{ccc}-7x+8y=-18&\text{multiply both sides by 4}\\4x-9y=-3&\text{multiply both sides by 7}\end{array}\right\\\\\underline{+\left\{\begin{array}{ccc}-28x+32y=-72\\28x-63y=-21\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad\qquad-31y=-93\qquad\text{divide both sides by (-31)}\\.\qquad\qquad\boxed{y=3}\\\\\text{Put the value of y to the second equation}\\\\4x-9(3)=-3\\4x-27=-3\qquad\text{add 27 to both sides}\\4x=24\qquad\text{divide both sides by 4}\\\boxed{x=6}$