標題:
Maths questions
發問:
1)*Please write the equations and the steps* peter buys some $2 stamps and some $5 stamps. If she spends $54 altogether and gets 15 stamps, how many $2 stamps does she buy? 2) Why are 3r and 1/r unlike terms?
最佳解答:
1. Let x be the number of $2 stamps Peter bought then (15 - x) is the number of $5 stamps bought Total value = 54 So, 2x + 5(15 - x) = 54 2x + 75 – 5x = 54 -3x = -21 x = 7 So, he bought 7 $2 stamps 2. Consider the power of 3r and 1 / r The power of r in 3r is 1 However, the power of r in 1 / r is -1 Therefore, they are unlike terms.
其他解答:
1)Let $2 stamps be x, $5 stamps be y. x + y = 15..............(1) 2x + 5y = 54...........(2) (1)x2, 2x + 2y =30.........(3) (2)-(3), 3y = 24 y = 8 sub. y=8 into (1), x + 8 = 15 x = 7 therefore, she buy 7 $2 stamps and 8 $5 stamps. 2) If 3r and 1/r are in the equation below: 3r + 1/r = 0 r ( 3r + 1/r ) = 0 3r*2 + 1 = 0 as 3r*2 is not equal to 1, therefore, 3r and 1/r are unlike terms.
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