Answer:B
Step-by-step explanation:
Answer:
1. figure 4
2. Figure 1
3. Figure 3
Step-by-step explanation:
1. r is the degree of the line or group of dots that makes a line. for r=1, the line is going to be as close to a linear line as possible. the dots will be close together a make either a close or perfect straight line. This is why we pick figure 4, because the points are decently close together and form a positive slope.
2. a linear relationship can be tested by a straight line test, and in this case you pick the figure that fails the test the most. in this case, Figure 1 fits.
3. looking for r=-1 is looking for the opposite of r=1, so since figure 3 is the opposite of figure 4, we know it fits the description
First term ,a=4 , common difference =4-7=-3, n =50
sum of first 50terms= (50/2)[2×4+(50-1)(-3)]
=25×[8+49]×-3
=25×57×-3
=25× -171
= -42925
derivation of the formula for the sum of n terms
Progression, S
S=a1+a2+a3+a4+...+an
S=a1+(a1+d)+(a1+2d)+(a1+3d)+...+[a1+(n−1)d] → Equation (1)
S=an+an−1+an−2+an−3+...+a1
S=an+(an−d)+(an−2d)+(an−3d)+...+[an−(n−1)d] → Equation (2)
Add Equations (1) and (2)
2S=(a1+an)+(a1+an)+(a1+an)+(a1+an)+...+(a1+an)
2S=n(a1+an)
S=n/2(a1+an)
Substitute an = a1 + (n - 1)d to the above equation, we have
S=n/2{a1+[a1+(n−1)d]}
S=n/2[2a1+(n−1)d]
