Core 1
Edexcel Core 1 Revision
- Created by: Rebecca Youngs
- Created on: 12-01-12 12:35
Simultaneous equations by
elimination:
2x+3y= 8 you need to get the x's or y's to match
3x-y=23 x3 to get 3y in both equations as they both +/- you add
2x+3y =8
6x-3y= 69
11x= 77 /11
x=7 now you put x=7 into original equation
(2x7) +3y=8
14+3y= 8
3y=8-14 (-6) /3
y=12
Simultaneous equations by
substitution:
x+2y= 3 make either x or y the subject of either equation + substitute
x2+3xy=10
x=3-2y substitute into 2nd equation
(3-2y)2 + 3(3-2y)y = 10
9+4y2-12y +(9-6y)y = 10
9+4y2-12y + 9y-6y2 = 10
-2y2-3y+9 = 10
2y2+3y+1 = 0 factorise
(2y+1)(y+1)
y=-1/2 or -1 now pick easier first equation and sub in ys to find x values
Inequalitites (< or >)
Bigger than > Smaller than <
1. When you multiply or divide an inquality by a negative number, you need to change the inquality sign to its opposite e.g.
12-3x<27 minus 12
-3x<15 divide by -3 FLIP
x>-5
2. To solve a quadratic inequality you:
-solve the corresponding
-sketch the graph of the quadratic function
-use your sketch to find the required set of values
Equalities
Sometimes you need to find the set of values for x when two inequalities are true together.. USE A NUMBER LINE!
Find the set of values of x for which:
3x-5<x+8 & 5x>x-8 Hollow dots on a number line= < or >
2x-5<8 4x>-8 Solid dots on a number line=<(or same as)>
2x<13 x>-2
x<6.5
-4 -------3-------2-------1-------0------1-------2-------3-------4------5------6------7-------8
o------------------------------------------------------------------------------->
<-----------------------------------------------------------------------------------------o
so the required set of values are -2<x<6.5
Straight Lines
Straight lines equation: y=mx+c m= gradient c= y intercept (where line crosses y)
If the gradient is positive the line will go up in a right diagonal line like /
If the gradient is negative the line will do down like \
e.g. what is the gradient and y intercept of 3y+2x=5?
3y=5-2x
y=5/3-2/3x
y=-2/3x+5/3
gradient= -2/3x and y intercept=5/3
parrallel lines have the same gradient.
= length between two points
Gradient of a line connecting 2 coordinates
equation: y1-y2 / x1-x2 or y2-y1/ x2-x1 y is always on top
e.g. (2, 6) & (5, 9)
9-6 / 5-2
3/3
=1
y=1x+c
Finding the intercept
Once you've found your gradient sub it into y=mx+c
e.g. (2, 6) & (5, 9)
9-6 / 5-2
3/3
=1
y=1x+c
pick either coordinates and sub in it y and x (2, 6)
6=1x2+c
c=4
y=1x+4
Midpoint
x co ordinate if midpoints= x1+x2 / 2
y co ordinate of midpoints= y1+y2 /2
e.g. (4, 7) & (8, 9)
(4+8)/2 (7+9)/2
=6 =8
Midpoint: (6,8)
Perpendicular Lines
A number times by it's reciprocal is always one
-5 = -1/5
0 does not have a reciprocal.
The gradient of a line x the gradient of it's perpendicular line always equals -1
e.g. y=3x+2
gradient of perpendicular = -1/3 (becomes negative also when it flips over)
we have the line y=2x+3
the line perpendicular goes through (0,5) Find the equation of the perpendic line
gradient= -1/2x+c
y=-1/2x+5 (as 5 is the y intercept)
Crossing points of 2 lines
Find where y=2x+1 and y=3x+5 cross
2x+1 = 3x+5 -2x
1=x+5 -5
x= -4
2x-4+1=-7
y=-7
crossing point = (-4,-7)
Arithmetic Sequences
These have to go up or down by the same amount each time
equation: nth term= a+(n-1)d
a= starting number d= common difference
e.g.
4,7,10,13...
a=4 d= 3 as increasing by 3 each time
nth term= 4+(n-1)3
=4+3n-3
=3n+1
Arithmetic Sequence Exam Question
The 3rd term in a sequence is 20 and the 7th term is 12.
Find a and d.
3rd 7th
a+2d=20 a+6d=12
put in a similtaneous equation and work out by elimination
a+2d=20 x3 3a+6d=60 as both are +s you -
a+6d=12 a+6d=12
2a =48 /2
a =24
24+2d=20 -24
2d=-4 /2 d = -2
Sum of Arithmetic series
Formula: Sn= 1/2n (a+L) or Sn= [2a+(n-1)d]
1) Find the sum of the first 100 odd numbers
1 + 3 + 5+... a=1 d= 2
1/2x100[2x1+(100-1)2]
50[2+(99x2)]
50 x 200= 10,000
2) Salary= £15,000 Rise= £1,000peryear Max Salary= £25,000
a) how much did she earn in her first eight years? b) 14 years?
15+16+17+18+19+20+21+22 =£148,000
b) (a) +23+24+25+25+25+25 =£295,000 repeat 25,000 because that is the max.
Differentiation
Tangents are straight lines that touch a curve at a single point. A normal is perpendicular to a tangent at the same point.
General Rule: dy/dx = nxn-1
e.g. y=x3 = 3x2
we use this to find the gradent of curves at different points
To find the gradient of different points: e.g. y=x2 at x=5
1. Differentiate equation of the curve
dy/dx= 2x
2. Sub in x value of point you want to know gradient of
2x5=10
=10
Tangents and Normals
Whenever you find a gradient of a curve using dy/dx you also get the gradient of a tangent.
eg. find the equation of a tangent to the curve y=2x2+4x at point (1,6)
1) find dy/dx 4x+4
2) find gradient of curve (sub in x=1) 4x1+4= 8
3) use y=mx+c to find equation of tangent (m=8)
y=8x+c
6=8x1+c
c=-2
y=8x-2
Second Derivatives
d2y / dx2 means differentiate and then differentiate again
f(x) is a function
f '(x) means dy/dx
f ''(x) means d2y / dx2
e.g. Find d2y/dx of 3x3+ 2x2 -3/x
3x3+2x2-3x-1
dy/dx= 9x2+4x+3x-2
d2y/dx2= 18x+4-6x-3
Intergration
Intergration finds y when you have dy/dx
Add 1 to the power and then divide by the new power number
e.g.
dy/dx= 3x2
3x3 /3
=x3 +C remember the C!!
Finding the constant of intergration
Given that f-1(x) = x2-2 / x1/2 and that curve C for f(x) passes through the point (4,5), find the equation for C
f-1(x) = x2/ x1/2 - 2/ x1/2
=x3/2-2x-1/2
intergrate as usual
x5/2 / 5/2 -2x1/2 / 1/2 + c
f(x) 2/5x5/2 -4x1/2 + c
sub in (4,5)
5=2/5x45/2 -4x41/2 + c
5=64/5-8+c add 8 13=64/5 +c
c= 13-64/5 (13-12^4/5) c=1/5 y=2/5x5/2-41/2+1/5
Discriminant
Seen by exam question laid out as ax2 + bx + c
If there are real roots b2-4ac>0 will have two roots (touch x axis twice)
If the roots are equal b2-4ac=0 will have one root (touch the x axis once)
If there are no real roots b2-4ac<0 will have no real roots (won't touch x axis)
Related discussions on The Student Room
- What topic are you on at school in Further maths yr 12? »
- Core pure 1 vs 2 »
- Self-teaching A-Level Further Mathematics in One Month Blog »
- A level further maths modules (edexcel) »
- BSC Maths Module Options »
- Only 46 candidates nationally did FS1 and FS2? »
- I feel like I screwed up. »
- How can i sit A level further maths? »
- Trampoline Exercises That Will Challenge Your Body »
- What happens if...? »
Comments
Report
Report