SOLUTION: a number increased buy 3 time the square root is 28. what is this number

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Question 125682: a number increased buy 3 time the square root is 28. what is this number
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let n = the number
n+%2B+3%2Asqrt%28n%29+=+28
3%2Asqrt%28n%29+=+28+-+n
square both sides
9n+=+784+-+56n+%2B+n%5E2
n%5E2+-+65n+%2B+784+=+0
use quadratic formula
n+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
n+=+%28-%28-65%29+%2B-+sqrt%28+%28-65%29%5E2-4%2A1%2A784+%29%29%2F%282%2A1%29+
n+=+%2865+%2B-+sqrt%284225+-+3136+%29%29+%2F+2+
n+=+%2865+%2B-+sqrt%28+1089+%29%29+%2F+2+
n+=+%2865+%2B+33%29+%2F+2
n+=+49
n+=+%2865+-+33%29+%2F+2
n+=+16 answer
check answer
n+%2B+3%2Asqrt%28n%29+=+28
16+%2B+3%2Asqrt%2816%29+=+28
16+%2B+3%2A4+=+28
28+=+28
n+=+49 only works if you SUBTRACT 3 times the square root from number
n+%2B+3%2Asqrt%28n%29+=+28
49+-+3%2Asqrt%2849%29+=+28
49+-+21+=+28
28+=+28