SOLUTION: can you please explain how you work these out. i would be gratful if you show your working out clearly so that i understand it. 2) multiply and simplify : x(2x+8)-x(x-3)

Algebra ->  College  -> Linear Algebra -> SOLUTION: can you please explain how you work these out. i would be gratful if you show your working out clearly so that i understand it. 2) multiply and simplify : x(2x+8)-x(x-3)       Log On


   

Question 397982: can you please explain how you work these out. i would be gratful if you show your working out clearly so that i understand it.

2) multiply and simplify :
x(2x+8)-x(x-3)
2π(R^2 -r ^2)

factorise common factor:
20x - 35
2x^2 +6
12y^2 - 4YX+20x^2Y
2πrh + 2πr^2
solve the follwoing equations
2(x-1)=3
7r+2=5(r-4)
Solve simultaneous equations algebraically and draw a graph.
a)Y = 2x
Y= x + 5
b)3x + y = 13
2x – 3y = 6
c)2x + 3y = 7
3x – 2y = 17

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
multiply and simplify :
x(2x+8)-x(x-3)
= 2x^2+8x-x^2+3
= x^2+8x+3
---------------------------------------
2π(R^2 -r ^2)
= 2(pi)(R-r)(R+r)
---------------------------------------
Factorise common factor:
20x - 35 = 5(4x-7)
--------------------------
2x^2 +6 = 2(x^2+3)
--------------------------
12y^2 - 4YX+20x^2Y
= 4(3y^2-xy+5x^2)
--------------------------
2πrh + 2πr^2 = 2(pi)r(h+r)
--------------------------

solve the following equations
2(x-1)=3
(x-1) = 3/2
x = 1+(3/2)
x = 5/2
--------------------------
7r+2=5(r-4)
7r+2 = 5r-20
2r = -22
r = -11
--------------------------
Solve simultaneous equations algebraically and draw a graph.
a)Y = 2x
Y= x + 5
---
Substitute for y and solve for "x":
2x = x + 5
x = 5
---
Then y = 2x = 2*5 = 10
Solution (5,10)
graph%28400%2C300%2C-10%2C10%2C-10%2C10%2C2x%2Cx%2B5%29
--------------------------------------------
b)3x + y = 13
2x – 3y = 6
---
Multiply thru the 1st equation by 3 to get:
9x+3y = 39
2x-3y = 6
----
Add and solve for "x":
11x = 45
x = 45/11
------
Solve for "y":
3x + y = 13
3(35/11) + y = 13
(105/11) + y = (13*11/11)
y = 38/11
--=
graph%28400%2C300%2C-10%2C10%2C-10%2C10%2C-3x%2B13%2C%282%2F3%29x-2%29
--------------------------------------------------------
c)2x + 3y = 7
3x – 2y = 17
---
Multiply thru 1st by 3.
Multiply thru 2nd by 2.
---
6x + 9y = 21
6x - 4y = 34
---
Subtract and solve for "y":
-13y = 13
y = -1
---
Solve for "x":
2x+3y = 7
2x+3(-1) = 7
2x = 10
x = 5
----------


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Cheers,
Stan H.