Answer:
3 miles
Step-by-step explanation:
to find the amount of miles it is to the library you have to find how many miles it is when the minutes are zero
so when x = 0 what is y
0 + 7y = 21
7y = 21
y is 3
so that means the library is 3 miles away from his house
Answer:

Step-by-step explanation:
Perform the multiplication and addition:

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<em>Comment on the squaring</em>
There are several ways you can find the square (x+4)².
- Use your knowledge that (x+a)² = x²+2ax+a².
- Use FOIL* to compute (x+4)(x+4) = x² +4x +4x +4² = x²+8x+16
- Use the distributive property: (x+4)(x+4) = x(x+4) +4(x+4) = x² +4x +4x +4² (same as FOIL for two binomials)
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* FOIL is mnemonic for {First, Outer, Inner, Last} referring to pairs of terms in the factors (x +a)(x +b). The x terms are the First terms. The Outer terms are the first x and b. The Inner terms are "a" and the second x. The Last terms are "a" and "b". You are to form the sum of those pairs of terms to find the product of the binomials.
Answer:
x=1000 or 10 to the 3rd power