Question 233197: 1. If a varies directly as b and a=1.2, when b=1.5, find a when b=20.
3. If y varies directly as x, and y=3.14 when x=180, find the value if y when x=360.
7. Given that y varies directly as the square of x. The graph of this relation is a
(1)straight line
(2)circle
(3)parabola
(4)hyperbola
9. The graph of all points with coordinates (x,y) such that y vaies directly as x is
(1)a hyperbola, only
(2)a parabola
(3)sometimes a straight line and sometimes a hyperbola
(4)a straight line though the origin
These are the 4 questions i need help with please show steps.
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! 1. If a varies directly as b and a=1.2, when b=1.5, find a when b=20.
a = kb is direct variation formula.
a = 1.2 when b = 1.5 becomes 1.2 = k*1.5
this means that k = 1.2/1.5 = .8
if b = 20, the formula becomes a = .8*20 = 16
3. If y varies directly as x, and y=3.14 when x=180, find the value if y when x=360.
y = kx is the direct variation formula.
y = 3.14 when x = 180 becomes 3.14 = k*180.
this means that k = 3.14 / 180 = .017444444
when x = 360, y = .017444444 * 360 = 6.28
7. Given that y varies directly as the square of x. The graph of this relation is a
(1)straight line
(2)circle
(3)parabola
(4)hyperbola
I would say parabola.
direct variation is y = kx where k is the constant of proportionality.
If k = 1, then you get y = x^2.
The standard form of a quadratic equation is y = ax^2 + bx + c.
If b and c are equal to 0, and a = 1, you get y = x^2.
A quadratic equation is the equation of a parabola.
Since a is positive, the parabola opens upward.
Here's a graph of y = x^2
9. The graph of all points with coordinates (x,y) such that y vaies directly as x is
(1)a hyperbola, only
(2)a parabola
(3)sometimes a straight line and sometimes a hyperbola
(4)a straight line though the origin
I would say a straight line through the origin.
y varies directly with x means that y = kx where k is the constant of proportionality.
if k = 1, the equation is y = x.
this is the equation of a straight line through the origin as shown below:
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