2007-05-25 06:40:18 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
z^2 - 2z - 15 = 0
( z - 5 ) ( z + 3 ) = 0
z-5 = 0 and z + 3 = 0
z = 5 and z = - 3
2007-05-25 06:46:24 · answer #1 · answered by muhamed a 4 · 1⤊ 0⤋
z^2-2z-15=0
=> z^2+3z-5z-15=0
=>z(z+3)-5(z+3)=0
=>(z+3)(z-5)=0
z= -3 or 5
.
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2007-05-25 15:08:44 · answer #2 · answered by alpha 7 · 0⤊ 0⤋
(z-5)(z-3) = 0
z = 5 or z = 3
25 - 10 - 15 = 0
9 + 6 - 15 = 0
Z = 5 or 3
2007-05-25 13:47:18 · answer #3 · answered by Anonymous · 1⤊ 0⤋
(z-5)(z+3)=0
z=5 or -3
2007-05-25 16:25:20 · answer #4 · answered by Dave aka Spider Monkey 7 · 0⤊ 0⤋
z^2-2z-15=0
D=(-2)^2 -4*1*(-15)=4+60=64
D^(1/2)=8
x1=(-(-2)+D^(1/2))/2=(2+8)/2=10/2=5
x2=(-(-2)-D^(1/2))/2=(2-8)/2=(-6)/2=-3
2007-05-25 16:27:45 · answer #5 · answered by im_loosing_my_mind_1985 2 · 0⤊ 0⤋