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F.1 maths數學 Liner Equations in One Unknown

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p.212.One number is 18 greater than another number. If the smaller number is subtracted from three times the greater number, the result is 78. Find the sum of the two numbers.3.ABCD is a square. If AB=3x+3 and BC=5x-11, find the area of the square.4.If a triangle has height (10-2x) cm, base 9 cm and area... 顯示更多 p.21 2.One number is 18 greater than another number. If the smaller number is subtracted from three times the greater number, the result is 78. Find the sum of the two numbers. 3.ABCD is a square. If AB=3x+3 and BC=5x-11, find the area of the square. 4.If a triangle has height (10-2x) cm, base 9 cm and area (7-x) cm2, find the value of x.

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2. Let a be the greater number and (a-18) be the smaller number. 3a-(a-18)=78 3a-a+18=78 2a=60 a=30 Hence, the smaller number is (30-18) = 12 Therefore, the sum of the two numebrs is 30+12=42. 3. Let x be the length of the suqare. Since ABCD is a square , AB=BC 3x+3=5x-11 2x=14 x=7 Therefore, the area of the suqare = x^2 =7^2 =49 cm^2 4. 9(10-2x) ------------ = 7-x 2 90-18x = 14-2x 76 = 16x x = 4.75

其他解答:

1. x=smaller y=larger y-x=18 (1) 3y-x=78 (2) from (1), y=18+x (3) sub (3) to (2) 3(18+x)-x=78 .....
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