Unit 15.3 More about Straight-lines

Unit 15.3 More about Straight-lines

Rearrange straight-line equations to the form  $y=mx+c$  

Multiple Choice

Given $5x-3y=15$ , the gradient is _ and the  $y$ - intercept is _.  

•  $5,\ 15$  

•  $-5,\ 15$  

•  $\frac{5}{3},\ -5$  

•  $\frac{3}{5},\ 5$  

Make $y$ the subject first 

•  $5x-3y=15$  

•            $3y=5x-15$  

•              $y=\frac{5}{3}x-5$  

•  $\therefore m=\frac{5}{3},\ c=-5$  

Fill in the Blanks

Express  $x+y+20=0$ in the form of  $y=mx+c$ .

Fill in the Blanks

Express  $y=3\left(x+5\right)$ in the form of  $y=mx+c$ .

Multiple Choice

Express  $x-5y=40$ in the form of  $y=mx+c$ .

•  $y=8-5x$  

•  $y=\frac{1}{5}x-8$  

•  $y=5x-8$  

Multiple Choice

Find the gradient and  $y$ - intercept of   $x-5y=40$ .

•  $\frac{1}{5},\ -8$ 

•  $y=\frac{1}{5}x-8$  

•  $5,\ -8$  

Intercepts a.k.a points on the axes.

• Sub in $x=0\ \rightarrow\ y$ intercept 

• Sub in $y=0\ \rightarrow\ x$ intercept 

Find the coordinates where $-x+y=1$ cross the axes.

When  $y=0,\$  $-x+0=1$ 
                                     $x=-1$                                    $\therefore\ \left(-1\ ,\ 0\right)$   

Find the coordinates where $-x+y=1$ cross the axes.

When  $x=0,\$  $-0+y=1$ 
                                     $y=1$                                    $\therefore\ \left(0\ ,\ 1\right)$   

Multiple Select

Where does $3x+5y=45$ cross the axes? 

• (0, 9)

• (0, 15)

• (9, 0)

• (15, 0)

Multiple Select

Where does $2y=20-x$ cross the axes? 

• (10, 0)

• (0, 10)

• (0, 20)

• (20, 0)

Multiple Select

Where does $12x+6y=-60$ cross the axes? 

• (-10, 0)

• (0, -10)

• (-5, 0)

• (0, -5)