Question 397982
multiply and simplify : 
x(2x+8)-x(x-3)
= 2x^2+8x-x^2+3
= x^2+8x+3
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2π(R^2 -r ^2)
= 2(pi)(R-r)(R+r)
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Factorise common factor: 
20x - 35 = 5(4x-7)
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2x^2 +6 = 2(x^2+3)
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12y^2 - 4YX+20x^2Y
= 4(3y^2-xy+5x^2)
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2πrh + 2πr^2 = 2(pi)r(h+r)
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solve the following equations 
2(x-1)=3
(x-1) = 3/2
x = 1+(3/2)
x = 5/2
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7r+2=5(r-4)
7r+2 = 5r-20
2r = -22
r = -11
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Solve simultaneous equations algebraically and draw a graph. 
a)Y = 2x
Y= x + 5
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Substitute for y and solve for "x":
2x = x + 5
x = 5
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Then y = 2x = 2*5 = 10
Solution (5,10)
{{{graph(400,300,-10,10,-10,10,2x,x+5)}}}
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b)3x + y = 13
2x – 3y = 6
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Multiply thru the 1st equation by 3 to get:
9x+3y = 39
2x-3y = 6
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Add and solve for "x":
11x = 45
x = 45/11
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Solve for "y":
3x + y = 13
3(35/11) + y = 13
(105/11) + y = (13*11/11)
y = 38/11
--=
{{{graph(400,300,-10,10,-10,10,-3x+13,(2/3)x-2)}}}
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c)2x + 3y = 7
3x – 2y = 17
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Multiply thru 1st by 3.
Multiply thru 2nd by 2.
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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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{{{graph(400,300,-10,10,-10,10,(-2/3)x-(7/3),(3/2)x-(17/2))}}}
 
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Cheers,
Stan H.