r^2+3r=8
how to you go about solving this?
2007-08-03 06:41:32 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
r² + 3r - 8 = 0
r = [ - 3 ± √(9 + 32) ] / 2
r = [- 3 ± √41 ] / 2 is exact answer.
Approximate answer is:-
r = [ - 3 ± 6.4 ] / 2
r = 1.7 , r = - 4.7
2007-08-03 07:14:55 · answer #1 · answered by Como 7 · 0⤊ 0⤋
we can write, r^2+3r=8 as
r^2+3r - 8 = 0. Since this is a quadratic equation, you can use the quadratic formula to solve for r.
2007-08-03 06:48:48 · answer #2 · answered by valkyrie 1 · 0⤊ 0⤋
r^2 +3r = 8
Set the quadratic equal to 0:
r^2 +3r -8 = 0
Now, plug into the quadratic formula x=[-b+/- (b^2 - 4ac)^(1/2)]/(2a)
a=1 b=3 c=-8
r=[-3 +/- ((-3)^2 -4*1*(-8))^.5]/(2*1)
r=[-3 +/- (9+32)^.5]/2
r=-3/2 +/- 41^.5 / 2
2007-08-03 06:45:32 · answer #3 · answered by lockedjew 5 · 0⤊ 0⤋
put the 8 on the other side of the equal sign (so it should now look like a formula you can use the quadratic formula on: r^2 + 3r -8= 0 ) now, you can either complete the square or use the quadratic formula.
2007-08-03 06:51:16 · answer #4 · answered by satirev 2 · 0⤊ 0⤋