By applying basic property of Geometric progression we can say that sum of 15 terms of a sequence whose first three terms are 5, -10 and 2 is
<h3>What is
sequence ?</h3>
Sequence is collection of numbers with some pattern .
Given sequence

We can see that

and

Hence we can say that given sequence is Geometric progression whose first term is 5 and common ratio is -2
Now
term of this Geometric progression can be written as

So summation of 15 terms can be written as

By applying basic property of Geometric progression we can say that sum of 15 terms of a sequence whose first three terms are 5, -10 and 2 is
To learn more about Geometric progression visit : brainly.com/question/14320920
Answer:
A,D, and E are the answers on E2020
If triangles PQR and STU are similar then PQ corresponds to ST and PR corresponds to SU. Therefore, PQ/ST=PR/SU
Considering that, PQ= 7-x, ST= 13-x, PR= x²+5 and SU= x² +20
therefore, (7-x)/(13-x)= (x²+5)/(x²+20)
cross multiplying,
7x² +140-x³+20x =13x²+65-x³-5x
combining the like terms,
6x² +15x -75=0
solving for x,
x = 5/2 or -5