A) Solve y=f(x) for x.
This instruction just means to manipulate the equation so that x is all by itself on one side. We can use a mixture of addition/subtraction and multiplication/division to do this with any equation.
f(x)=-3x+7
y=-3x+7
y-7=-3x
(y-7)/-3=x
b) Find the input to f(x) when the output is -8.
This means that it wants us to find the x value that provides a y value of -8. To solve this, we just need to plug -8 in for y and solve for x.
y=-3x+7
-8=-3x+7
-15=-3x
x=5
First of all we have to find the slope
m = y₂-y₁ / x₂-x₁
m = -8 + 16 / -10 + 8
m = 8/-2
m = -4
y-y₁ = m (x-x₁)
y + 8 = -4 (x + 10)
y + 8 = -4x - 40
y = -4x -40 - 8
y = -4x -48
Line up the equations and add them up, adding the x's together then y's (which should cancel out) then the totals.
Then the equation should equal -9x=36 and when tou solve x= -4.
Plug -4 in for x in one of the equations, I chose the second one, and solve.
y = -21
Hope this helps! :)
The correct answer is ) D 20
Hope This Helps
-Dante