<u>Question 8</u>
a^2 + 7a + 12
= (a+3)(a+4)
When factorising a quadratic, the product of the two factors should equal the constant term (12), and the sum of the two factors should equal the linear term (7). To find the two factors, list out the factors of 12 (1x12, 2x6, 3x4) and identify the pair that adds up to 7 (3+4).
An alternative method if you get stuck during your exam would be to solve it algebraically using the quadratic formula and then write it in the factorised form.
a = (-7 +or- sqrt(7^2 - 4(1)(12)) / 2(1)
= (-7 +or- sqrt(1))/2
= -3 or -4
These factors are the negative of the values that would go in the brackets when written in factorised form, as when a = -3 the factor (a+3) would equal 0. (If it were positive 3 instead, then in the factorised form it would be a-3).
<u>Question 10</u>
-3(x - y)/9 + (4x - 7y)/2 - (x + y)/18
Rewrite each fraction with a common denominator so you can combine the fractions into one.
= -6(x - y)/18 + 9(4x - 7y)/18 - (x + y)/18
= (-6(x - y) + 9(4x - 7y) - (x + y)) /18
Expand the brackets and collect like terms.
= (-6x + 6y + 36x - 63y - x - y)/18
= (29x - 58y)/18
= 29/18 x - 29/9 y
In this question, the first information that we get is that Kayla spent half of her weekly allowance in clothes. On cleaning the oven Kayla gets $4. Finally Kayla is left with $12.
Let us assume that the weekly allowance of Kayla = x
Amount of allowance saved after buying clothes = x/2
Then we can go for the equation
x/2 + 4 = 12
x + (4 * 2) = 12 * 2
x + 8 = 24
x = 24 -8
= 16
So we can now see that the weekly allowance of Kayla is $16
4c + 5h = 650 and
5c + 6h = 800 where c are chefs, h are helpers
Start by finding an expression for c
4c + 5h = 650
4c = 650 -5h
c = (650- 5h)/4
Then substitute that into the second equation and solve for a number value for h
5 (650-5h)/4 + 6h = 800
(3250-25h)/4 + 6h = 800
Multiply both sides by 4
3250-25h + 24h = 3200
-h = -50
h = 50
Take that 50 and substitute it into the expression we have for c to get a number value for c
C= 650-5(50)/4
C = 650-250/4
C = 400/4
C= 100
Check your first equations, substituting $50 for the helpers and $100 for the chefs.
4 (100) + 5(50) =
400 + 250 = 650
5(100) + 6(50) =
500 + 300 = 800
