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Paladinen [302]
1 year ago
14

The length of a rectangle is 5 cm more than twice a number. the width is 4cm less than the same number. if the area of the recta

ngle is 15cm2, find the number
​
Mathematics
1 answer:
lana [24]1 year ago
7 0
A = Lw (area of rectangle is length times width)
A = 15 (Area is 15)
L = 2x + 5 (length is 2 times a number plus another 5)
w = x - 4 (width is 4 less than that number

Plug in the values:
15 = (2x + 5)(x - 4)
FOIL
15 = 2x2 - 8x + 5x - 20
simplify:
15 = 2x2 - 3x - 20
Subtract 15
0 = 2x2 - 3x - 35
Factor out the quadratic. We know that one number has to be 7 and the other 5 so that they multiply together to make 35, and that one of them has to be negative so that it's actually -35.
That means we have m * n = -35
We also need it set up so that so that 2m + n = -3:
2 * -5 + 7 = -3
0 = (2x + 7)(x - 5)
So:
0 = 2x + 7, or 0 = x - 5
x = -7/2 or 5
We cannot have a negative length, so x = 5

Check:
15 = (2 * 5 + 5) (5 - 4)
15 = 15 * 1
15 = 15
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Answer:

\$180.55

Step-by-step explanation:

step 1

<u><em>Simple interest</em></u>

we know that

The simple interest formula is equal to

A=P(1+rt)

where

A is the Final Investment Value

P is the Principal amount of money to be invested

r is the rate of interest  

t is Number of Time Periods

in this problem we have

t=10\ years\\ P=\$2,250\\r=4\%=4/100=0.04

substitute in the formula above

A=2,250(1+0.04*10)

A=2,250(1.4)

A=\$3,150

step 2

<u><em>Interest compounded annually</em></u>

we know that    

The compound interest formula is equal to  

A=P(1+\frac{r}{n})^{nt}  

where  

A is the Final Investment Value  

P is the Principal amount of money to be invested  

r is the rate of interest  in decimal

t is Number of Time Periods  

n is the number of times interest is compounded per year

in this problem we have  

t=10\ years\\ P=\$2,250\\r=4\%=4/100=0.04\\n=1

substitute in the formula above

A=2,250(1+\frac{0.04}{1})^{1*10}  

A=2,250(1.04)^{10}  

A=\$3,330.55

step 3

Find the differences between the two final amounts

A=\$3,330.55-\$3,150=\$180.55

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Fiesta28 [93]
2f +4f +2 -3
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2f+4f+2-3 at f=3 would also be 17


8 0
2 years ago
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