2007-08-20 18:14:21 · 5 answers · asked by xxbabycheekzix 1 in Science & Mathematics ➔ Mathematics
(15 - b) (b) = 56
15b - b² = 56
b² - 15b + 56 = 0
(b - 7) (b - 8) = 0
b = 7 , b = 8
a = 8 , a = 7
2007-08-20 19:50:40 · answer #1 · answered by Como 7 · 2⤊ 0⤋
ab = 56___Equation 1
a + b = 15___Equation 2
From Equation 2,
a = 15 - b___Equation 3
Substitute Equation 3 into Equation 1,
(15 - b) (b) = 56
15b - b^2 = 56
b^2 - 15b + 56 = 0
(b - 7) (b - 8) = 0
b - 7 = 0 or b - 8 = 0
b = 7 or 8
From Equation 3
When b = 7
a = 15 - 7
a = 8
When b = 8
a = 15 - 8
a = 7
Therefore,
a = 7 ; b = 8
or
a = 8 ; b = 7
2007-08-20 19:55:04 · answer #2 · answered by 痴心情长剑 3 · 0⤊ 2⤋
ab=56
a=56/b
a+b=15
56/b+b=15
56+b*2=15b
b*2-15b+56=0
(b-8)(b-7)=0
b=8 or b=7
hope this helps
2007-08-20 18:29:24 · answer #3 · answered by Madotta 1 · 0⤊ 0⤋
7 and 8 because:
7 x 8 = 56
7+8 = 15
=]
if you like my answer pick it as best?
2007-08-20 18:24:14 · answer #4 · answered by ... 4 · 0⤊ 0⤋
7,8
2007-08-20 18:22:01 · answer #5 · answered by Cyrus Y 1 · 0⤊ 0⤋