Q. y=−x(x+6)+18y=−7x+12If (a,b) is a solution to the system of equations shown and b<0, what is the value of a ?
Write equations: Write down the system of equations.We have the following system of equations:1) y=−x(x+6)+182) y=−7x+12
Set equations equal: Set the two equations equal to each other to find the x-values where their y-values are the same.−7x+12=−x(x+6)+18
Expand quadratic equation: Expand the quadratic equation on the right side.−7x+12=−x2−6x+18
Rearrange and combine terms: Rearrange the equation to set it to zero and combine like terms. x2+x−6=0
Factor quadratic equation: Factor the quadratic equation. (x+3)(x−2)=0
Solve for x-values: Solve for the x-values that make the equation true.x+3=0 or x−2=0x=−3 or x=2
Determine negative y-value: Determine which x-value corresponds to a negative y-value b < 0.We need to plug x=−3 and x=2 into either of the original equations to find the corresponding y-values.Let's use the second equation y=−7x+12.For x=−3: y=−7(−3)+12=21+12=33For x=2: y=−7(2)+12=−14+12=−2
Choose x-value with negative y: Since we are looking for the x-value where y (or b) is negative, we choose x=2 because it gives us y=−2, which is less than 0.Therefore, the value of a is 2.
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