Solve the system by substitution. {:[-4x-y=21],[y=3x]:} (◻,◻)

Substitute y with 3x: Substitute y with 3x in the first equation. Given the second equation y = 3x, we can substitute y in the first equation -4x - y = 21 with 3x. -4x - (3x) = 21Combine and solve for x: Combine like terms and solve for x. -4x - 3x = 21 -7x = 21Divide to find x: Divide both sides by -7 to find the value of x. -7x / -7 = 21 / -7 x = -3Substitute x to find y: Substitute x back into the second equation to find y. Using the second equation y = 3x and substituting x with -3: y = 3(-3) y = -9Write as ordered pair: Write the solution as an ordered pair (x, y). The solution is (-3, -9).

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Solve the system by substitution.

{:[-4x-y=21],[y=3x]:}

(◻,◻)

Solve the system by substitution. $\newline$ $\begin{aligned} -4 x-y & =21 \\ y & =3 x \end{aligned}$ $\newline$ $(\square, \square)$

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Algebra 2

Solve a system of equations in three variables using substitution

Full solution

Q. Solve the system by substitution.

\newline

\begin{aligned} -4 x-y & =21 \\ y & =3 x \end{aligned}

\newline

(\square, \square)

Substitute $y$ with $3x$ : Substitute $y$ with $3x$ in the first equation. $\newline$ Given the second equation $y = 3x$ , we can substitute $y$ in the first equation $-4x - y = 21$ with $3x$ . $\newline$ $-4x - (3x) = 21$
Combine and solve for x: Combine like terms and solve for x. $\newline$ $-4x - 3x = 21$ $\newline$ $-7x = 21$
Divide to find x: Divide both sides by $-7$ to find the value of x. $\newline$ $-7x / -7 = 21 / -7$ $\newline$ $x = -3$
Substitute $x$ to find $y$ : Substitute $x$ back into the second equation to find $y$ . Using the second equation $y = 3x$ and substituting $x$ with $-3$ : $y = 3(-3)$ $y = -9$
Write as ordered pair: Write the solution as an ordered pair $(x, y)$ . $\newline$ The solution is $(-3, -9)$ .