6hrs = 360 minutes
360/7.5 = 48 bottles required
500g = 0.5kg
48x0.5 = 24 kg
24x 5 = 120p
1. x^2 + 13x + 36 = 0
using powerful & time-sparing quadratic formula :
delta = 13^2 - 4*1*36 = 25 = 5^2
x1 and x2 = (-13 -/+ 5)/2 = -9 and -4
x^2 + 13x + 36 = (x+9)(x+4)
2. other way : complete the square
b^2 + 12b + 32 = b^2 + 2*6b + 6^2 - 6^2 + 32
b^2 + 12b + 32 = (b+6)^2 - 4
b^2 + 12b + 32 = (b+6-2)(b+6+2) = (b+4)(b+8)
3. other way : -4 "ovious" solution : (-4)^2 - (-4) -20 = 0
so the other is : -4 . a2 = -20/1 ---> a2 = 5
a^2 - a - 20 = (a-5)(a+4)
True or false it will be true
Short answer: 100
I assume you want to find x.
We want an equation that says that x is equal to 105cm, minus that 5 percent, because that is his height before the 5% was added. That looks like:
x + 0.05x = 105
(0.05 is 5% in decimal form, which is necessary in equations like this).
x + 0.05x = 1.05x
1.05x = 105.
Isolate x by dividing both sides by 1.05
1.05x / 1.05 = x, 105 / 1.05 = 100
x = 100, so he was 100cm tall before summer
My original answer was 99.75. This is wrong because I used the 5% of 105, which is wrong because in the question it says his original height (which is x) had 5% added to it. So its 5% of x, not 5% of 105. This changes the whole equation.
