y is proportional to x^2. When y=45, x=3. Find a formula for y in terms of x.
If y is proportional to x then you can write y=kx^2 where k is a constant you are trying to find. Then substitute in the values you have been given for x and y. This gives you 45=k(3)^2. Then work to solve this to find k. 45=k(9)k=45/9. Therefore k=5. You can now put your value for k into the formula to give you an answer of y=5x^2.
AP
Related Maths GCSE answers
All answers ▸Clare buys some shares for $50x. Later, she sells the shares for $(600 + 5x). She makes a profit of x% (a) Show that x^2 + 90x − 1200 = 0
(2x+3)/(x-4) - (2x-8)/(2x+1) = 1 Solve for x
John wants to invest £100 into a savings account for 15 years. If he invests in saving account A he will receive 3.5% simple interest and if he invests in savings account B he will receive 3% compound interest. Which account should he choose and why?
25* 3/2