The sum of two numbers **a** and **b** is 20. Write an expression for the sum of their squares, in terms of **a.**

weredumbmaster22 Sep 28, 2021

#2**+1 **

I used your tip and im stuck. I got:

a+b=20

10+10=20

and..

b=20-a

10=20-10

So when it asks "Write an expression for the sum of their squares, in terms of **a**." I wrote **b=20-a **and 10=20-10 but the answer still is wrong. Do you know where i was wrong?

weredumbmaster22 Sep 28, 2021

#4**+1 **

a^2+b^2 would be 10^2+10^2 which is 100+100 and the answer is 200. Its wrong.

weredumbmaster22 Sep 28, 2021

#5**+2 **

a and b are unknown.

you keep saying a=10 and b=10 but that is only one of an infinite number of possibilities.

a could be 8 and b 12

or a could be 5.3 and b could be 14.7

or a could be pi and b could be 20-pi

What you know is that a+b=20 which means b=20-a

You want the sum of their squares is a^2 +b^2 but we have to replace b with 20-a

so

\(a^2+b^2\\ =a^2+(20-a)^2\\ =a^2+400+a^2-40a\\ =2a^2-40a+400\)

Melody
Sep 28, 2021