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secondary 4 | E Maths
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Date Posted: 2 years ago
Views: 366
They did not say that y is directly proportional to x, so you CANNOT write y = kx.
Twice of the square of x means twice of x², or in short 2x².
So, y is directly proportional to 2x². We can write this as
y = p(2x²) where p is a constant of proportionality
y = 2px²
or simply
y = kx² (since 2p is a constant of proportionality in itself).
When x is increased by 50%, the new value of x is now 150% of the old value of x, so the new value of x is "1.5x".
Using the proportionality equation y = kx², we get the following.
New value of y
= k (new value of x)²
= k (1.5x)²
= k (2.25x²)
= 2.25kx²
= 2.25 times the old value of y
= 225% of the old value of y
So, the percentage increase in y is 225% - 100% = 125%.
Twice of the square of x means twice of x², or in short 2x².
So, y is directly proportional to 2x². We can write this as
y = p(2x²) where p is a constant of proportionality
y = 2px²
or simply
y = kx² (since 2p is a constant of proportionality in itself).
When x is increased by 50%, the new value of x is now 150% of the old value of x, so the new value of x is "1.5x".
Using the proportionality equation y = kx², we get the following.
New value of y
= k (new value of x)²
= k (1.5x)²
= k (2.25x²)
= 2.25kx²
= 2.25 times the old value of y
= 225% of the old value of y
So, the percentage increase in y is 225% - 100% = 125%.
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It is same as the method in the comment.
Date Posted:
2 years ago
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y becomes 2.25 the initial when x increase by 50% (1.5x), y has increased by 1.25, which is 125%
Date Posted:
2 years ago
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