Please help me with this maths question, i'm really baffed!!!

Find the points of intersection of the line 2X + 3Y = 12 with the axes

Find also the gradient of this line

I know one of the intersections is (0,4), but how do I work out the other one.

And my workings made -2/3 the gradient, but apparently it is -4/6, why is this?
why would I lose marks for answering this?

Please help.........I could really do with the help :frown:

Reply 1

Mechie

15

-2/3 is just -4/6 simplified.

For the intersection of the line with the Y-axis, make y=0 then solve for x.

Reply 2

LPat

rearrange to make y the subject : y= -2/3x + 4
using y = mx + c (0,4) is the y intercept
x intercepts occur when y = 0

0=-2/3x + 4
2/3x = 4
x = 6

so axis intercepts are (0,4) & (6,0)

Reply 3

lost15

OP

Original post by davidmarsh01

-2/3 is just -4/6 simplified.

For the intersection of the line with the Y-axis, make y=0 then solve for x.

but the mark scheme said that -2/3 is wrong

Reply 4

R3L4Y

1

Original post by lost15

but the mark scheme said that -2/3 is wrong

-2/3 = -4/6

now usually in gradient type questions you don't simplify ..but...in the end..it is the same

(edited 13 years ago)

Reply 5

R3L4Y

1

tip: when an equation is in the form :

y= mx + n

then that

n

will always be your y-axis intercept.

Reply 6

lost15

OP

Hey Guys thanks, I get that now!!!

But does anybody understand the second part of this question

Solve the equation 2X² +3X=0

i got X= 0 or = -3/2

Part 2, I do not understand 2X² +3X - k =0 has no real roots

Please help me with this, I really appresciate it. You people are way nicer than my maths teacher

Find the set of values of k for which the equation

Reply 7

username458263

9

Original post by lost15

Hey Guys thanks, I get that now!!!

But does anybody understand the second part of this question

Solve the equation 2X² +3X=0

i got X= 0 or = -3/2

Part 2, I do not understand 2X² +3X - k =0 has no real roots

Please help me with this, I really appresciate it. You people are way nicer than my maths teacher

Find the set of values of k for which the equation

For the equation to have no real roots,

b^2 -4ac < 0

. Sub in the values and solve.

What level are you? This question seems like Scottish Higher (AS), but the one above seems more like GCSE-level. I suppose the English system might just be different.

Reply 8

MostCompetitive

2

No real roots so

b^2-4ac<0

. So

9-8k<0

. So

k>\frac98

(edited 13 years ago)

Reply 9

username458263

9

Original post by MostCompetitive

No real roots so

b^2-4ac<0

. So

9-8k<0

.

This is true, but you shouldn't give full solutions, just try to show the person what approach to take. This actually applies to someone else above as well.

Reply 10

MostCompetitive

2

Original post by derangedyoshi

For the equation to have no real roots,

b^2 -4ac < 0

. Sub in the values and solve.

What level are you? This question seems like Scottish Higher (AS), but the one above seems more like GCSE-level. I suppose the English system might just be different.

This is all AS level mathematics (these topics are covered in the first AS unit), and y=mx+c is GCSE level but still in the AS C1 books

(edited 13 years ago)

Reply 11

lost15

OP

Original post by MostCompetitive

No real roots so

Unparseable latex formula:

b^2-4ac<0

. So

Unparseable latex formula:

9-8k<0

. So

Unparseable latex formula:

k>\frac98

I'll have you know that I got 8A*s at GCSE and I fully intend to get A's in all of my A Levels.
Do you know why I do well, because when I need help I'm not afraid to ask for it. Thank you for your cynicism and negativity, I 'll harness it for good.