Answer:
6. Since, by given graph,
The end behavior of the function f(x),
![f(x)\rightarrow -\infty\text{ if }x\rightarrow -\infty](https://img.qammunity.org/2020/formulas/mathematics/middle-school/j6d6f8yzzh3hzlp30krudm3zel7ysuwvel.png)
![f(x)\rightarrow +\infty\text{ if }x\rightarrow +\infty](https://img.qammunity.org/2020/formulas/mathematics/middle-school/7xchfmocgm7mzj9a430fhimmy15ertrd3c.png)
Thus, the function f(x) must has odd number of roots ( where the graph of a function intersects the x-axis )
⇒ The function must has odd number of solutions,
Again by the graph,
Graph of the function intersects the x-axis 5 times ( it touches the origin so it have the repeated root of x = 0 ),
Hence, the total number of real solution of f(x) is 5.
7. Let x represents the width of the rectangle( in inches ),
Given,
The length is 10 inches longer than the width,
⇒ Length of the rectangle = ( x + 10 ) inches
Thus, the area of the rectangle,
A = length × width = x(x+10)
According to the question,
A = 144 in²
⇒ x(x+ 10) = 144
![x^2+10x=144](https://img.qammunity.org/2020/formulas/mathematics/middle-school/7vlephcvabqsv6prjyjki1jid8qdljaj0f.png)
![x^2+10x-144=0](https://img.qammunity.org/2020/formulas/mathematics/middle-school/fftck06hos9sgqzl6vrg5wq58wjpuhbd9m.png)
( Middle term splitting )
![x(x+18)-8(x+18)=0](https://img.qammunity.org/2020/formulas/mathematics/middle-school/bdi28xpcs3y83fw9i6sscxv4dzw1itxh23.png)
![(x+18)(x-8)=0](https://img.qammunity.org/2020/formulas/mathematics/middle-school/htfug32hc0rg5y6ui6yv354z8l9qmkmsbs.png)
⇒ x = -18 or x = 8 ( By zero test property )
The width can not be negative,
Hence, the width of the rectangle would be 8 inches.