Q. 8x−y=122x−6y=3Consider the system of equations. If (x,y) is the solution to the system, then what is the value of x+y ?
Write Equations: Write down the system of equations.We have the following system of equations:{:\begin{align*}8x-y&=12\2x-6y&=3\end{align*}:}
Multiply Second Equation: Multiply the second equation by 3 to make the coefficients of y the same.Multiplying the second equation by 3, we get:\begin{align*}
8x-y&=12,\
6x-18y&=9
\end{align*}
Eliminate y: Subtract the second equation from the first equation to eliminate y.Subtracting the second equation from the first, we get:(8x−y)−(6x−18y)=12−9This simplifies to:8x−y−6x+18y=3Combining like terms, we get:2x+17y=3
Solve for y: Solve for y using the modified second equation.We can solve for y by rearranging the modified second equation:2x+17y=317y=3−2xy=173−2x
Substitute for y: Substitute the expression for y back into the first original equation to solve for x.Substituting y=173−2x into the first original equation 8x−y=12, we get:8x−173−2x=12Multiplying through by 17 to clear the fraction, we get:136x−(3−2x)=204
Correct Multiplication: Step 5 (Correction): Correct the multiplication to clear the fraction.Multiplying through by 17 to clear the fraction, we get:17×8x−17×17(3−2x)=17×12This simplifies to:136x−(3−2x)=204Now distribute the negative sign inside the parentheses:136x−3+2x=204Combine like terms:138x−3=204Add 3 to both sides:138x=207Divide both sides by 138:x=138207Simplify the fraction:x=1.5
Substitute for x: Substitute the value of x back into the expression for y. Now that we have x=1.5, we can substitute it back into the expression for y: y=173−2xy=173−2(1.5)y=173−3y=170y=0
Find x+y: Add the values of x and y to find x+y.x+y=1.5+0x+y=1.5