What is the value of this sigma notation?

[ukumure]

Hi, I'm currently a Grade 11 student and I need help for this question (Precalculus):

If \sum_(i=1)^(50) f(i)=90 and \sum_(i=30)^(50) g(i)=60, what is the value of \sum_(i=1)^(50) (7 g(i)-f(i)+12)/(2)?



P.S. To those who could answer this, it would be a great help for me! Thank you so much!

 

[JeffM]

Let's go step by step

[MATH]\text {If } \sum_{i=1}^m h(i) = p, \text { then} \sum_{j=1}^m \{a * h(i))\}[/MATH] = WHAT? WHY?

 

[lev888]

Hi, I'm currently a Grade 11 student and I need help for this question (Precalculus):

If \sum_(i=1)^(50) f(i)=90 and \sum_(i=30)^(50) g(i)=60, what is the value of \sum_(i=1)^(50) (7 g(i)-f(i)+12)/(2)?

View attachment 24286

P.S. To those who could answer this, it would be a great help for me! Thank you so much!

Properties of Sigma Notation

Properties of Sigma Notation - Cool Math has free online cool math lessons, cool math games and fun math activities. Really clear math lessons (pre-algebra, algebra, precalculus), cool math games, online graphing calculators, geometry art, fractals, polyhedra, parents and teachers areas too.

www.coolmath.com

 

[ukumure]

Let's go step by step

[MATH]\text {If } \sum_{i=1}^m h(i) = p, \text { then} \sum_{j=1}^m \{a * h(i))\}[/MATH] = WHAT? WHY?

Thank you! Helps a bit

 

[ukumure]

Properties of Sigma Notation

Properties of Sigma Notation - Cool Math has free online cool math lessons, cool math games and fun math activities. Really clear math lessons (pre-algebra, algebra, precalculus), cool math games, online graphing calculators, geometry art, fractals, polyhedra, parents and teachers areas too.

www.coolmath.com

Thank you for sharing the link! Would really help me

 

[Steven G]

Hi, I'm currently a Grade 11 student and I need help for this question (Precalculus):

If \sum_(i=1)^(50) f(i)=90 and \sum_(i=30)^(50) g(i)=60, what is the value of \sum_(i=1)^(50) (7 g(i)-f(i)+12)/(2)?

View attachment 24286

P.S. To those who could answer this, it would be a great help for me! Thank you so much!

I will help any 11th grader taking precalculus. Good for you.

I will do a similar problem.

[math]If\ \sum_{i=1}^{25} f(i) =20\ and\ \sum_{i=1}^{25} g(i) = 40, then\ what\ is\ the\ value\ of\ \sum_{i=1}^{25} [3f(i) + 2g(i)][/math]?

[math]\sum_{i=1}^{25} [3f(i) + 2g(i)] = \sum_{i=1}^{25}3f(i) + \sum_{i=1}^{25}2g(i) = 3\sum_{i=1}^{25} f(i) + 2\sum_{i=1}^{25}g(i) = 3(20) + 2(40) = 140[/math]

 

[topsquark]

I think the problem ukumure is having is that the sum over g(i) only goes from i = 30 to i = 50, not from i = 1 as the f(i) summation has.

-Dan

 

[ukumure]

I will help any 11th grader taking precalculus. Good for you.

I will do a similar problem.

[math]If\ \sum_{i=1}^{25} f(i) =20\ and\ \sum_{i=1}^{25} g(i) = 40, then\ what\ is\ the\ value\ of\ \sum_{i=1}^{25} [3f(i) + 2g(i)][/math]?

[math]\sum_{i=1}^{25} [3f(i) + 2g(i)] = \sum_{i=1}^{25}3f(i) + \sum_{i=1}^{25}2g(i) = 3\sum_{i=1}^{25} f(i) + 2\sum_{i=1}^{25}g(i) = 3(20) + 2(40) = 140[/math]

Thank you for this example! It totally eased my confusion!

 

[JeffM]

I think the problem ukumure is having is that the sum over g(i) only goes from i = 30 to i = 50, not from i = 1 as the f(i) summation has.

-Dan

Oh. I failed to notice. My error. I think that is a problem.

 

[ukumure]

I think the problem ukumure is having is that the sum over g(i) only goes from i = 30 to i = 50, not from i = 1 as the f(i) summation has.

-Dan

Exactly, my confusion. But already got the problem! Thanks for helping me out! ?

 

[topsquark]

Exactly, my confusion. But already got the problem! Thanks for helping me out! ?

The Forum where (apparently) got your solution from did not recognize the error in the summation limits.

-Dan

 

[Deleted member 4993]

The Forum where (apparently) got your solution from did not recognize the error in the summation limits.-Dan

One way to "get" the problem would be - to have the instructor to retract it!!