During an NFL game, a camera hangs from a cable stretched in a straight line above the field. A punt flies through the air along a parabola. Does the ball ever touch the cable, and if so, where? Finding the crossing points means solving a system in which one equation is not linear. By the end of this page you will know how to answer that question, and how to handle circles, hyperbolas, exponentials, logs and radicals too.
What is a non-linear system?
The main method is the same one you used in Integrated Math I: isolate a variable in the simplest equation and substitute into the other one. If both equations are already solved for $y$, just set the two expressions equal.
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Solve the following non-linear system, which represents the intersection between a parabola and a line: $y = x^2 - 4x + 3$ $y = x - 1$
Solve the following non-linear system, which represents the intersection between a parabola and a line:
Some systems tell you the sum and the product of two numbers, or something that leads to them. These are called symmetric systems: swapping $x$ and $y$ leaves the system unchanged.
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The sum of two positive numbers is $10$ and the sum of their squares is $58$. Set up a non-linear system of equations and solve it to find these numbers.
The sum of two positive numbers is $10$ and the sum of their squares is $58$. Set up a non-linear system of equations and solve it to find these numbers.
A rectangular plot has a perimeter of $40$ ft and an area of $96$ sq ft$^2$. Set up a non-linear system of equations to calculate the dimensions of the plot and solve it.
A rectangular plot has a perimeter of $40$ ft and an area of $96$ sq ft$^2$. Set up a non-linear system of equations to calculate the dimensions of the plot and solve it.
In a right triangle, the hypotenuse measures $13$ inches and the total perimeter is $30$ inches. Set up a system of equations to determine the length of the two legs.
In a right triangle, the hypotenuse measures $13$ inches and the total perimeter is $30$ inches. Set up a system of equations to determine the length of the two legs.
The circular orbit of a satellite in a frame of reference follows the equation $x^2 + y^2 = 25$, while the trajectory of a comet describes the hyperbola $xy = 12$. Solve…
The circular orbit of a satellite in a frame of reference follows the equation $x^2 + y^2 = 25$, while the trajectory of a comet describes the hyperbola $xy = 12$. Solve the system to find the exact coordinates of the points of intersection of both trajectories.
In this course $\log x$ means $\log_{10} x$. Use the product and quotient rules to combine logs into one, then rewrite as an exponential equation. Always check the domain at the end.
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Determine the solution of the logarithmic system, applying the properties of logarithms: $\log x + \log y = 1$ $x - y = 3$
Determine the solution of the logarithmic system, applying the properties of logarithms:
Solve the following radical system, making sure to check which solutions are valid by analyzing the domain of the radicals: $\sqrt{x^2 - y^2} = \sqrt{33}$ $x + y = 11$
Solve the following radical system, making sure to check which solutions are valid by analyzing the domain of the radicals:
Many "quantity = rate × amount" stories give a product equation. If a change in one factor changes the other, you get a second product equation, and the pair is a non-linear system.
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A cyclist completes a journey of $60$ miles at a constant speed. If they had traveled $2$ mph faster, they would have taken $1$ hour less to complete the route. Set up…
A cyclist completes a journey of $60$ miles at a constant speed. If they had traveled $2$ mph faster, they would have taken $1$ hour less to complete the route. Set up and solve a non-linear system to find the average speed $v$ and the time $t$ taken.
A group of friends decides to buy a birthday present that costs $\$120…
A group of friends decides to buy a birthday present that costs $\$120$, dividing the payment equally. At the last minute, two more friends join the group, which reduces each person's share by $\$3$. Set up and solve a system to find how many friends there were initially and how much each paid.
When both equations are products of the same unknowns, dividing one equation by the other can cancel unknowns right away.
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A cylindrical sheet metal tank has an internal volume of $54\pi$ cubic feet and a lateral area (excluding the bases) of $36\pi$ square feet. Set up a system to find the…
A cylindrical sheet metal tank has an internal volume of $54\pi$ cubic feet and a lateral area (excluding the bases) of $36\pi$ square feet. Set up a system to find the base radius $r$ and the height $h$ of the cylinder, and solve it.
A principal $C$ is invested at an annual compound interest rate $r$ (expressed as a decimal). At the end of the first year, the amount generated is $\$11000…
A principal $C$ is invested at an annual compound interest rate $r$ (expressed as a decimal). At the end of the first year, the amount generated is $\$11000$. At the end of the second year, the amount rises to $\$12100$. Set up a non-linear system to calculate the initial principal $C$ and the interest rate $r$, and solve it.
A line can cut a curve in two points, touch it in exactly one point (it is tangent), or miss it completely. When the system has a parameter, substituting leaves a quadratic whose discriminant $\Delta = b^2 - 4ac$ decides how many real solutions there are.
Back to the football. Set the parabola equal to the cable's line. You get a quadratic. If $\Delta > 0$, the ball crosses the cable twice (going up and coming down). If $\Delta = 0$, it just grazes the cable. If $\Delta < 0$, the ball never reaches it.
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Discuss for which values of the parameter $k$ the following system has exactly one solution (this is geometrically equivalent to the condition of tangency between the…
Discuss for which values of the parameter $k$ the following system has exactly one solution (this is geometrically equivalent to the condition of tangency between the circle and the line):