How do you solve 21n ^ { 2} + 5n - 6= 0?
2 Answers
Mar 28, 2018
Explanation:
Given:
Now, If :
And If :
Hence Explained.
Mar 28, 2018
Explanation:
"factorise the quadratic using the a-c method"
"that is factors of "21xx-6=-126" which sum to "+5
"the factors of "-126" which sum to + 5 are + 14 and - 9"
color(blue)"split the middle term using these factors"
rArr21n^2+14n-9n-6=0larrcolor(blue)"factor by grouping"
rArrcolor(red)(7n)(3n+2)color(red)(-3)(3n+2)=0
"take out the common factor "(3n+2)
rArr(3n+2)(color(red)(7n-3))=0
"equate each factor to zero and solve for n"
3n+2=0rArrn=-2/3
7n-3=0rArrn=3/7