Question

Please help asapp three questions 72 pts

Answer 1

`x^2-11x=x^2-2x\cdot5.5+5.5^2-5.5^2=(x-5.5)^2-30.25\\\\=(x-5.5)^2-30(1)/(4)=(x-5.5)^2-(121)/(4)\\\\\boxed{Answer:\ n=(121)/(4)}`



`9x^2-21=0\ \ \ |+21\\\\9x^2=21\ \ \ \ |:9\\\\x^2=(21)/(9)\to x=\pm\sqrt{(21)/(9)}\\\\\boxed{Answer:\ 1.53,\ -1.53}`



`x^2+2x=15\\\\x^2+2x\cdot1=15\ \ \ |+1^2\\\\\underbrace{x^2+2x\cdot1+1^2}_((a+b)^2=a^2+2ab+b^2)=15+1^2\\\\(x+1)^2=16\to x+1=\pm√(16)\\\\x+1=-4\ \vee\ x+1=4\ \ \ |-1\\\\\boxed{Answer:\ x=-5,\ x=3}`