2007-11-08 10:27:30 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
x^2-8x-20= (x-4)^2 -36 =0
x-4 = + or minus 6
x1 =10
x2= -2
2007-11-08 10:31:18 · answer #1 · answered by Anonymous · 0⤊ 0⤋
x^2 - 8x - 20 = 0
(x - 10) (x + 2) = 0
*When two things are multiplyed to make 0 1 of them must be 0*
x = 10 or x = -2
2007-11-08 10:33:45 · answer #2 · answered by bigbaddom1989 3 · 0⤊ 0⤋
We write
(x + ) (x + )
we look at factors of 20
1 20 added togther 21 subtracted 19
2 10 added together 12 subtracted 8
4 5 added together 9 subtracted 1
we see that 2 and 10 subtracted gives us the middle term -8x
10 needs to be negative and 2 is positive.
2007-11-08 10:41:02 · answer #3 · answered by Anonymous · 0⤊ 0⤋
=(x-10)(x+2)
so x = 10 and -2
2007-11-08 10:31:58 · answer #4 · answered by ironduke8159 7 · 0⤊ 0⤋
You can see that 2 and 10 are factors of 20, and one of them has to be multiplied by -1.
2-10=-8
so
(x²-8x-20)=(x+2)(x-10)
2007-11-08 10:33:16 · answer #5 · answered by DWRead 7 · 0⤊ 0⤋
-b+ or - square root of (b^2-4ac)/ 2a
8+/- square root of (64-4(1)(-20)/ 2a
8+/- square root of (64+80)/ 2
8+/- square root of (144) / 2
8+/- 12/ 2
8+ 12 / 2 8-12/2
20/2 -4/2
x= 10 x= -2
=)
2007-11-08 10:41:00 · answer #6 · answered by Anonymous · 0⤊ 0⤋
use the quadratic formula ax^2+bx=c=0
so a=1 b=-8 c=-20
x=-b(+/-)(b^2-4ac)^(1/2) / 2a
=8(+/-)(64-(4x1x-20)^(1/2) /2x1
=8(+/-)(144)^(1/2) /2
=8(+/-)12 /2
two answers x=8+12 /2=10
and x=8-12 /2=-2
2007-11-08 10:34:26 · answer #7 · answered by mlbabe03 2 · 0⤊ 0⤋