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Example 2. The length of a rectangle is 7 more than the width. Its area is 30. Find the dimensions of the rectangle. x x + 7 A = 30 A = lw 30 = x(x + 7)

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Presentation on theme: "Example 2. The length of a rectangle is 7 more than the width. Its area is 30. Find the dimensions of the rectangle. x x + 7 A = 30 A = lw 30 = x(x + 7)"— Presentation transcript:

1 Example 2. The length of a rectangle is 7 more than the width. Its area is 30. Find the dimensions of the rectangle. x x + 7 A = 30 A = lw 30 = x(x + 7) 30 = x 2 + 7x = x 2 + 7x – 30 0 = ( )( ) Use the x-box to factor the trinomial if you can’t do it in your head. x + 10 x – 3 0 = x = x x – 3 = x = 3 Reject -10 because you cannot have a negative dimension. reject Answer: Length = = 10 Width = 3

2 Example 3. Kara has two sisters. One of the sisters is 7 years older than Kara. The other sister is 3 years younger than Kara. The product of Kara's sisters' ages is 24. How old is Kara? (Hint: let x = Kara’s age, and use the sentence in the problem to write an equation to solve.) Let: x = Kara’s age x – 3 = youngest sister’s age x + 7 = oldest sister’s age (x – 3)(x + 7) = 24 x 2 + 7x – 3x – 21 = 24 x 2 + 4x – 21 = x 2 + 4x – 45 = 0( )( ) = 0 x + 9 x – 5 x + 9 = x = - 9 x – 5 = x = 5 reject Answer: Kara is 5

3 1)Let x = a number x = 6x -6x -6x x 2 – 6x + 8 = 0 Put into standard form: ax 2 + bx + c then factor. 2)Let x = a number x 2 – 15 = 2x -2x -2x x 2 – 2x – 15 = 0 Put into standard form: ax 2 + bx + c then factor. 3) Let x = a number 2x 2 + x = x 2 + x – 6 = 0 4)Let x = a number 4x 2 – 7 = x 2 – 25 = 0 5) Let x =1 st CI x + 1 = 2 nd CI x(x + 1) = 56 x 2 + x = x 2 + x – 56 = 0


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