Question

which term of the progression 20 , 19 1/4 , 18 1/2 , 17 3/4 is the first negative term ?

Answer 1

It's a decreasing sequence. Let's find the number of term which will be zero. Then the next integer will give negative term.

answer and equating an to zero.

a = 20 , d = -3/4

an = a+(n-1)d

= 20+(n-1)(-3/4)

= 20+(-3n+3)/4

= (80-3n+3)/4

83 - 3n = 0

3n - 83 = 0

n = 83/3

n = 27.66

The next integer is 28

So 28th term will be the first -ve term....

Answer 2

Answer:

Given- an=20 , d=-3/4

an=a+(n-1)d

0 = 20 + (n-1) (-3/4)

0 = 20 + (-3n+3)/4

Taking LCM :

0 = (80-3n+3)/4

80 - 3n + 3 = 0

-3n + 84 = 0

Taking - sign common

-(-3n + 84) = 0

3n - 84 = 0

3n = 84

n = 84/3

n = 27.66

Round 27.66 to the nearest whole number = 28

So n=28

Step-by-step explanation: