the sum of the 10th and 11th terms of an arithmetic sequence is 65 what is the sum of its first 20th terms
1 answer:
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Make equal to zero
add7 both sides
8m^2+7m-8=0
quadratic fomrula
if you have
ax^2+bx+c=0
x=
8m^2+7m-8=0
a=8
b=7
c=-8
x=
x=
x=
x=
or x=
aprox
x=-1.52902 or 0.654016
add7 both sides
8m^2+7m-8=0
quadratic fomrula
if you have
ax^2+bx+c=0
x=
8m^2+7m-8=0
a=8
b=7
c=-8
x=
x=
x=
x=
aprox
x=-1.52902 or 0.654016