Let's make an equation. So let's have t as our mystery number. The word "is" shows where the equal sign will be. Let's find out what the first half of the equation will be. Twice the square of a certain positive number. 2t² Now the second half. 144 more than twice the number. 2t+144 2t²=2t+144 Let's subtract 2t from both sides. 2t²-2t=144 Let's divide both sides by 2. t²-t=72 By looking at the equation, I can tell that it is less than 10. The number may be 9. 81-8=72 The number is 9. Let's plug it in. 2(81)=144+18 162=162 There's also another way to solve it by plugging in two expressions on a calculator and searching for when they intercept (shown in a picture below). The number is 9.
