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What times what equals -72 but adds to get -34? Solve the equation by factoring- 3x^2-34x-24=0

User Mrsoltys
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2 Answers

5 votes
First part:
-36 * 2 = -72
-36 + 2 = -34

Second part: Assuming that the 3x^2 is positive...(the answers are bolded)
3x^2-34x-24=0
(x-12)(3x+2)=0
x-12=0 3x+2=0
+12 +12 -2 -2
x=12 3x=-2

(3x)/(3)= (-2)/(3)
x=
(-2)/(3)
User Dzavala
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6.9k points
6 votes
OK SO THE THING WE HAVE TO FACTOR DOESN"T RELATE TO THE PROBLEM

easy way to solve is factor -72 and find what factos add up so 34
-72=
1,-72=-71 no
2,-36=-34 correct
therefor the numbers are 2 and -36
that was easy
now the legit math way

so

xy=-72
x+y=-34

x+y=-34
subtract x
y=-34-x
subsitute
x(-34-x)=-72
-34x-x^2=-72
add 34x+x^2 to bboth sides
0=x^2+34x-72
factor
facotr -72 and find what 2 factors add up to 34
-2 and 36 add up to 34

(x-2)(x+36)=0
set each to zero
x-2=0
add 2
x=2

x+36=0
subtract 36
x=-36

the numbers are 2 and -36




Second question
factor 3x^2-34x-24 which has nothing to do with the problem except ahthat 3 times 24=72



we do is we factor the first term
3=1 times 3
we know that it will be in a form liike
(somethingx+something)(somethingx+something) so
we put the 1 and 3 for the first somethings
(3x+ something)(1x+something)
then we factor 24
24=1 and 24 or 2 and 12 or 3 and 8 or 4 and 6
let's pick a random pair
2 and 12
they have to be different signs since the last term is negative
since midlde term is also negative, we know that bigge number is negative so
(3x+2)(x-12)
we expand
3x^2+2x-36x-24
3x^2-34x-24


ok, so I don't know what the equiqation was for but
numbers are 2 and -36
facotre form of equation that didn't relate=(3x+2)(x-12)
User Fabien Sa
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7.0k points