5n^2-3n-15=10

Question

competing the square to hard

Answer 1

5n²-3n-15=10,

5n²-3n-25=0,

n²-3n/5-5=0,

n²-3n/5+(3/10)²-(3/10)²-5=0, (completing the square)

(n-3/10)²-0.3²-5=0,

(n-0.3)²-5.09=0,

(n-0.3)²=5.09,

n-0.3=±√5.09,

n=0.3±√5.09,

n=0.3±2.2561 approx, n=2.5561 or -1.9561.