Solve by Table/Function Regression

Polynomial Multiplication on the SAT: Desmos Walkthrough

Graph both sides of the equation as

y=

curves and click the gray point where they cross to read the answer.

This lesson uses Desmos tables and regressions: drop the given values into a table, fit the model with a regression line, and read the constants straight off the fit.

Take this lesson interactively

A real SAT-style question

The function $p$ is defined by $p left parenthesis n right parenthesis equals 7 n cubed$ . What is the value of $n$ when $p (n)$ is equal to $56$ ?

$2$

$\frac{8}{3}$

$7$

$8$

How to solve it in Desmos, step by step

The idea

Graph both sides of the equation and click the gray point where they cross to read off n.

1
Step 1
Type this. Desmos draws the curve for the left side, 7 times n cubed.
Type in Desmos
$y=7x^{3}$
2
Step 2
Type this to add the horizontal line for 56, the value p of n equals.
Type in Desmos
$y=56$
3
Step 3
Click the gray point where the curve meets the line. Desmos shows the point 2 comma 56, so n equals 2, which is choice A.

The answer is A.

$2$

Now you try one

Same question type, different numbers. Use the exact Desmos moves from the walkthrough above.

The function

f

is defined by

f(x) = 9x^3

. What is the value of

x

when

f(x)

is equal to

72

Practice this with a live Desmos calculator

The interactive version of this lesson builds the Desmos graph up step by step as you click through, with a live calculator you can type into and your progress saved.

Open the interactive lesson

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