2007-02-02 08:04:06 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
assume a = y^2, then:
y^4 + 5y^2 - 84 = a^2 + 5a - 84
multiply to -84, add to 5: (12, -7)
(a + 12)(a - 7)=0
resub in y^2
(y^2 + 12)(y^2 - 7) = 0
y^2 + 12 = 0
y = +/- square root (-12)
y = +/- (square root 12) i
y^2 - 7 = 0
y = +/- square root 7
2007-02-02 08:09:30 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Since there is no equal sign I assume you want to factor the expression factors of the first term are Y^2
for the third term you need 2 numbers that when multiplied equal 84 but when added equal 5 also one of these must be negative because the 84 is negative. the factors 7 and 12 will work. The middle term of the given expression is positive therefore the largest of the factors must be positive.
(y^2 - 7)(y^2 + 12) are the factors.
2007-02-02 16:25:19 · answer #2 · answered by bignose68 4 · 0⤊ 0⤋
y^4 + 5y^2 - 84 >>12 - 7 = 5 and 12x7 = -84
= y^4 + 12y^2 - 7y^2 - 84
= y^2(y^2 + 12) - 7(y^2 + 12)
= (y^2 + 12)(y^2 - 5)
2007-02-02 16:13:22 · answer #3 · answered by Sheen 4 · 0⤊ 0⤋
(y^2-7)(y^2+12)
2007-02-02 17:22:18 · answer #4 · answered by Dave aka Spider Monkey 7 · 0⤊ 0⤋
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2007-02-02 16:11:53 · answer #5 · answered by Summer 5 · 0⤊ 2⤋