Solve a Quadratic Equation by COMPLETING THE SQUARE. To determine when the height of the ball is 336 feet. The distance along the ground from the bottom of the pole to the end of the wire is 4 feet greater than the height where the wire is attached to the pole. How far up the pole does the guy wire reach?Įxample 4: You throw a ball straight up from a rooftop 384 feet high with an initial speed of 3 feet per second. The functionĭescribes the height of the ball above the ground, s (t), in feet, t seconds after you threw it. The ball misses the rooftop on its way down and eventually strikes the ground. How long will it take for the ball to hit the ground? Eliminate any unreasonable answers.Įxample 2: Each side of a square is lengthened by 7 inches. The area of this new larger square is 81 square inches. Find the length of a side of the original square.Įxample 3: A guy wire is attached to a tree to help it grow straight. The length of the wire is 2 feet greater than the distance from the base of the tree to the stake. The height of the wooden part of the tree is 1 foot greater than the distance from the base of the tree to the stake.Įxample 5: A piece of wire measuring 20 feet is attached to a telephone pole as a guy wire. Step 6: Set each factor equal to 0. And solve the linear equation. Step 4: Write the equation in standard form. Substitute the given information to the equation. Step 3: Determine if there is a special formula needed. Step 1: Draw and label a picture if necessary. Let us work on one example to understand the factoring quadratic equations by taking the GCD(that is. In this method, the common numeric factor and the algebraic factors commonly shared by the components in the equation are determined and then the calculation is taken forward. Įxample 1: A vacant rectangular lot is being turned into a community vegetable garden measuring 8 meters by 12 meters. A path of uniform width is to surround garden. If the area of the lot is 140 square meters, find the width of the path surrounding the garden. Factoring Quadratic Equations by Factoring Greatest Common Divisor. of carpet.)Īrea of a rectangle and Landscaping/border/frame problems. Set each factor equal to 0. And solve the linear equation. Substitute the given information into the equation.Ħ. Determine if there is a special formula needed. Now we use our algebra skills to solve for "x".Steps for solving Quadratic application problems:ġ. Total time = time upstream + time downstream = 3 hours (to travel 8 km at 4 km/h takes 8/4 = 2 hours, right?) We can turn those speeds into times using: when going downstream, v = x+2 (its speed is increased by 2 km/h).when going upstream, v = x−2 (its speed is reduced by 2 km/h).Let v = the speed relative to the land (km/h)īecause the river flows downstream at 2 km/h:.Let x = the boat's speed in the water (km/h).There are two speeds to think about: the speed the boat makes in the water, and the speed relative to the land: What is the boat's speed and how long was the upstream journey? The negative value of x make no sense, so the answer is:Įxample: River Cruise A 3 hour river cruise goes 15 km upstream and then back again. The desired area of 28 is shown as a horizontal line. Let us solve this one by Completing the Square. How many you sell depends on price, so use "P" for Price as the variable what is the best price? And how many should you make? at $350, you won't sell any bikes at all.$700,000 for manufacturing set-up costs, advertising, etcīased on similar bikes, you can expect sales to follow this "Demand Curve":. Now you want to make lots of them and sell them for profit. You have designed a new style of sports bicycle! So the ball reaches the highest point of 12.8 meters after 1.4 seconds. Then find the height using that value (1.4) The method is explained in Graphing Quadratic Equations, and has two steps:įind where (along the horizontal axis) the top occurs using −b/2a: Note: You can find exactly where the top point is! The factors of −15 are: −15, −5, −3, −1, 1, 3, 5, 15īy trying a few combinations we find that −15 and 1 work Multiply to give a×c, and add to give b" method in Factoring Quadratics: There are many ways to solve it, here we will factor it using the "Find two numbers that It looks even better when we multiply all terms by −1: (Note for the enthusiastic: the -5t 2 is simplified from -(½)at 2 with a=9.8 m/s 2)Īdd them up and the height h at any time t is:Īnd the ball will hit the ground when the height is zero: Gravity pulls it down, changing its position by about 5 m per second squared: It travels upwards at 14 meters per second (14 m/s): (Note: t is time in seconds) The height starts at 3 m: Ignoring air resistance, we can work out its height by adding up these three things:
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