The Sum of first seven terms of an AP is 49 and the sum of first seventeen terms is 289 find the sum of first 20 terms

Spanish

2 answers:

Afina-wow [57]3 years ago

6 0

Answer:

S7=49

7/2(2a+6d)=49

2a+6d=49×2/7

2a+6d=14

2a=14-6d

a=7-3d........1

S17=289

17/2×(2a+16d)=289

2a+16d=289×2/17

2a+16d=34

a+8d=17

substituting value of a

7-3d+8d=17

5d=17-7

d=10/5=2

substituting value of d in equation 1

a=7-3×2=1

S20=20/2(2a+19d)=10(2×1+19×2)=10(40)

=40×10=400

zaharov [31]3 years ago

6 0

400 is right ^^^^^ it should be

You might be interested in

A Paula no le gusta la camiseta roja. Ella la camiseta blanca. * 1 point O preferir O prefiere O prefieres O prefieren

Mrac [35]

Prefiere is the correct answer

4 0

2 years ago

Read 2 more answers

What was her speed?

Ghella [55]

A) 0.1 mile per minute

<h2>Explanation:</h2>

From physics we know that distance, time and speed are related by the following equation:

$s=\frac{d}{t} \\ \\ s:Speed \\ \\ d:distance \\ \\ t:time$

So we can write the distance as:

$d=st$

Here we have a line that passes through the origin and whose<em> independent variable is t </em>and <em>dependent variable is d </em>and<em> the slope is s. </em>From the graph, we can calculate the equation of the line as:

$y=mx \\ \\ Finding \ slope \ m: \\ \\ m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}} \\ \\ (x_{1},y_{1})=(0,0) \\ \\ (x_{2},y_{2})=(10,1) \\ \\ m=\frac{1-0}{10-0} \\ \\ m=\frac{1}{10}$