word prob: sum of square of two cons. pos. odd integers, etc

[jshaziza]

1) The sum of the square of two consecutive positive odd integers is equal to 290. Find the two integers.

So far I have (x+y)^2=290 is this right and if so where do I go from here?

2) An object is thrown downward, with an initial speed of 16 ft/s, from the top of a building 480 feet high. How many secods later will the object hit the ground? Use the equation d=vt+16t^2, where d is the distance in feet, v is the initial speed, and t is the time in seconds.

My answer is 30 sec. but all I did was divide 480 by 16 istead of use the formula. Is my answer correct and if so can someone help me do it using the formula? Thx. for help on both problems.

 

[tkhunny]

Re: word prolblems

The sum of the square of two consecutive positive odd integers is equal to 290. Find the two integers. So far I have (x+y)^2=290 is this right and if so where do I go from here?

You back up are read the problem statement again.

"sum of the squares" is not the same as "square of the sum".

Try x^2 + y^2 = 290.

This is particularly important, since 290 isn't a perfect square.

 

[Denis]

Re: word prolblems

An object is thrown downward, with an initial speed of 16 ft/s, from the top of a building 480 feet high. How many secods later will the object hit the ground? Use the equation d=vt+16t^2, where d is the distance in feet, v is the initial speed, and t is the time in seconds. My answer is 30 sec. but all I did was divide 480 by 16 istead of use the formula. Is my answer correct and if so can someone help me do it using the formula?

Are you kidding? Have you missed most of your math classes?

Equation is d = vt + 16t^2 ; you're told d = 480 and v = 16; SO:
480 = 16t + 16t^2
16t^2 + 16t - 480 = 0 ; divide by 16:
t^2 + t - 30 = 0

If you can't solve that for t, you need classroom help.

 

[Mrspi]

Re: word prob: sum of square of two cons. pos. odd integers,

1) The sum of the square of two consecutive positive odd integers is equal to 290. Find the two integers.

So far I have (x+y)^2=290 is this right and if so where do I go from here?

Let x = the first of the integers
Then x + 2 = the second (since consecutive odd integers differ by 2)

The square of the first integer is x<SUP>2</SUP>.
The square of the second integer is (x + 2)<SUP>2</SUP>.

The SUM OF THE SQUARES is 290. So,

x<SUP>2</SUP> + (x + 2)<SUP>2</SUP> = 290

Now, solve for x.....that will be the first of the two integers; the second will be x + 2.

 

[jshaziza]

Who's equation is right Mrspi or tkhunny? I don't know which one to work with. :?

 

[stapel]

Who's equation is right Mrspi or tkhunny? I don't know which one to work with. :?

Study the two replies, and see how they relate. In particular, note how the variables and expressions are defined. The two equations are actually the same.

Eliz.