Q. y=x2+7x−7y=x+9If (x,y) is a solution to the system of equations and x<0, what is the value of y ?
Write equations: Write down the system of equations.We have the following system of equations:y=x2+7x−7y=x+9
Set equations equal: Set the two equations equal to each other to find the x-values where their y-values are the same.x2+7x−7=x+9
Subtract x: Subtract x from both sides to start solving for x.x2+7x−x−7=9x2+6x−7=9
Subtract 9: Subtract 9 from both sides to set the equation to zero.x2+6x−7−9=0x2+6x−16=0
Factor quadratic equation: Factor the quadratic equation.We are looking for two numbers that multiply to −16 and add up to 6. These numbers are 8 and −2.(x+8)(x−2)=0
Solve for x: Solve for x.Set each factor equal to zero and solve for x.x+8=0 or x−2=0x=−8 or x=2
Use x=−8: Since we are given that x < 0, we will use x=−8 and discard x=2.
Substitute x=−8: Substitute x=−8 into either of the original equations to find the corresponding value of y.Using the second equation y=x+9:y=(−8)+9y=1
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