Math Is Fun Forum

schr2002

Member

Registered: 2007-12-22

Posts: 1

please help me with a couple math problems

ok here are what the problems look like...

x-Intercept
2x+5y=20

Simplify
-7b+4a-6a-9b

Factor trinomial
y2-11y+30

Simplify
11x+4y2+6y2-2x

Equivalent to the inquality
2-5x74(2x-1)

Equivalent
15/x = 3/x-7
Please help me

luca-deltodesco

Member

Registered: 2006-05-05

Posts: 1,470

Re: please help me with a couple math problems

x intercept is when the line crosses the x axis -> y = 0

2x+5*0 = 20
x = 10

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collect like terms

(-7b-9b)+(4a-6a) = -16b-2a

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y²-11y+30 = (y-a)(y-b) -> why -a and -b? because the linear term is negative, and the constant positive.
ab = 30
a+b = 11

take the ab = 30, prime factors of 30 are 5,2,3. so you have 3 sets of possibilties for a and b
a = 10, b = 3
a = 15, b = 2
a = 5, b = 6

the only one of them that also works for a+b = 11 is (5,6) so thats the answer:

(y-5)(y-6) or other way round (y-6)(y-5)

i showed an analytical way to solve it, usually you can just think it through in your head to get the answer but if you have trouble this technique tends to work.

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collecting like terms again

11x-2x
4y²+6y²

so you have 9x+10y²

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what inequality? you havn't shown it anywhere

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15/x = 3/x - 7     multiply by x
15 = 3 - 7x    you can rearrange that however you like, i would put it as
7x + 12 = 0

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Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 46,340

Re: please help me with a couple math problems

1) x=(20-5y)/2

2)-2a-16b

3)y²-11y+30 = y²-6y-5y+30
= y(y-6)-5(y-6)
= (y-5)(y-6)

4) 11x+4y² +6y² -2x
= 9x+10y²

5) Question not clear

6)15/x = 3/x - 7

15/x = (3 - 7x)/x

15 = 3 - 7x

12 = -7x

x = -7/12

if the equation in the question is 15/x=3(x-7) then
15x-105=3x

12x = 105

x = 105/12 = 35/4

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schr2002

Member

Registered: 2007-12-22

Posts: 1

Re: please help me with a couple math problems

OMG thank you sooooo much